I'm developing a magic system that has as its weakness or limitation the fact that the energy used in the magic is drawn from the future. I'd like the system to experience a form of "resistance" such that the more influential the magic (lighting a candle vs. stopping time) the more difficult it is to pull the energy from the future, requiring greater concentration and fortitude on the part of the caster.

But the ultimate price paid for using the magic is something that occurs in the future. Magicians are tempted to use magic because the price doesn't appear to be paid today.

I am trying to choose between luck, heat, and life as the sources of magic. for example:

  • If drawn from luck, then a small spell may cause someone to trip in the vacinity of the cast spell sometime in the future.

  • If drawn from heat, the area around the caster would heat up in the future, possibly causing fire or damaging crops.

  • If drawn from life, something(s) living near where the spell was cast (plant, animal, or human) loses life (become ill for small spells, dies for large ones).

Question: Which energy source, drawn upon from the future, would be most believable?1 Luck, heat, or life?

A good answer should explain:

  • How the choice would reflect resistance as more energy or power is drawn for a spell.

  • How the choice would create a measurable or predictable consequence turning people against magic.

  • How the choice would be deterministic, meaning the aforementioned consequence could be traced back to a specific action.

Keep in mind this meta question about Magic being inherently POB. If you believe my question has fallen outside what was discussed there, please let me know and I'll improve the question.

1Yes, yes, yes, "believable" is wholly subjective based on the reader. You all know what I mean.

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    $\begingroup$ Why would drawing from heat cause an increase in heat later? Presumably you'd cool the future, extracting the heat energy to do something in the present? $\endgroup$ May 5, 2018 at 1:54
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    $\begingroup$ @ShadowRanger, you've brought up a good point, and I actually thought about the fact that it should generate cold, not heat, if I'm "drawing heat." But I left it as-is because (a) it's easier to visualize and (b) whatever arguments support the increase of heat also support it's decrease. $\endgroup$
    – JBH
    May 5, 2018 at 1:56
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    $\begingroup$ Well, just a heads up: Either way, it's not necessarily a cost of magic when you do this. Fundamentally, thermal differentials are an exploitable source of energy which can be harvested as temperatures equalize. I could see people intentionally casting ridiculously powerful spells to drive a turbine. The only real issue is how deterministically the "price" is paid; is the timeframe before it's paid predictable/controllable, or is there some randomized distribution? A distribution with likely fast turnaround, uncommon medium, and rare long delays seems reasonable as a defense against "abuse". $\endgroup$ May 5, 2018 at 2:03
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    $\begingroup$ You might like to look into Erfworld's Luckamancy. Any good luck (or positive effect) obtained now must be repaid in the future in the form of bad luck (or negative effects). $\endgroup$ May 5, 2018 at 2:38
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    $\begingroup$ Have you read the Heartstrikers books? The seers in that setting do precisely this. They trade one (set of) futures for another, at a terrible exchange rate. What happens when you trade away all possible futures? $\endgroup$ May 5, 2018 at 4:08

22 Answers 22


I'm going to agree with Flox, and say that Heat is the best choice. I'm going to go into a little more detail, though.

Both life and luck require something to be there in the future, and are difficult to create a traceable link. There are people with poor luck that might just trip without magic, and incredibly bad "luck" happens all the time. Similarly, with creatures getting ill or dieing, it can be hard to say why they died or became ill. Additionally, there's the issue of, for some creatures, scavengers coming and removing or consuming some or all of a corpse, making it difficult to see just why it died.

Heat, on the other hand? Heat works extremely well.

Heat is well known. We know why it starts, where it comes from, and how to prevent it - and have for thousands of years. Someone walking through a forest on a misty day shouldn't expect a random patch of grass to be on fire. Someone in a building shouldn't expect to see a scorch mark on the floor.

The distribution of heat can also leave a permanent mark, like a brand. Spells could create heated sigils or patterns - Something that might not be able to be spotted easily in nature, but could be seen in a more urban or rocky setting.

On the other hand, heat can be harvested. Heat can be measured. This means the "Downside" of magic can be mitigated. A college of wizards can have a set of spellcasting rooms - A wizard goes in, casts a spell, goes out, and some poor page has to sit and monitor the room until the expected heat event happens (Assuming a random or unknown amount of time before the heat happens). Then it's free to use again. Some clever engineering - and continuous and scheduled magicking - and this could be used to provide, say, hot water to the facility, or even neighboring buildings if there's enough magic going on. With big enough spells, you might even be able to build steam turbines.

As far as resistance goes - This is fairly straightforward. In electronics, resistors get hotter the more current you put through them. More magic makes more heat - And perhaps heat over a wider area. Want to cast a small spell? Use a small spell room. Want to cast a huge spell? Well, you'll need to use the gigantitorium designed for those spells, and there's a waiting list for that one since it's hard to build and contain.

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    $\begingroup$ How is it a good system if the price you pay is beneficial? $\endgroup$
    – Kami Kaze
    May 7, 2018 at 7:49
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    $\begingroup$ +1 for gigantitorium $\endgroup$
    – Daron
    May 7, 2018 at 8:28
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    $\begingroup$ You could mitigate the "good" by making the effect more random and semi-sentient. For example a casting room would stay dangerous for an indefinite time and could be generally triggered by someone, or even be slowly attracted to people of the same species as the caster entering the room. This would have the benefit of societal pressure on the wizards as casting a spell leaves the equivalent of a landmine behind. $\endgroup$
    – Borgh
    May 7, 2018 at 11:31
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    $\begingroup$ @KamiKaze On the other hand, how is it a bad system if the price you pay is beneficial? :) $\endgroup$
    – xDaizu
    Jul 18, 2018 at 9:01
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    $\begingroup$ Actually entropy (as in decay) would be even better then heat (as in agitation of the matter particles). Things oxidize, molecules break down into less energetic compounds, strutuctures crumble, unstable atoms decay spontaneously, living beings die. Also, all of it random. Many(if not all) of these decay events will be exotermic but there would be no (useful) heat - this energy was spent doing magic in the past. I expect that long term-large scale use of magic in planetary scale will have some pollution effects, like the rotting of useful uranium ores or oil fields. $\endgroup$
    – Geronimo
    Jul 19, 2018 at 0:38

"Heat", in the form of "extremes"

In Asimov's "The Gods Themselves" (which you might enjoy, as it fits your themes quite well, if from a sci-fi rather than a fantasy standpoint), one character describes energy as, roughly, "what you get from levelling out extremes". If you have a source of water up high, for instance, you can get energy out of it by letting it flow down over a turbine and join the rest of the water at sea level. If you have a hot thing, you can get energy out by cooling it down; if you have a cold thing, you can get energy out by heating it up.

This type of magic might draw magic from the heat and cold in the future. Rather than creating heat that could be used to power a turbine, for instance, a powerful spell might snuff out the fire someone was using to keep warm in the Arctic (and warm the surrounding environment by a fraction of a degree), or melt the ice that was preserving food in the summer (and cool the surrounding environment by a fraction of a degree).

Basically, in this form, magic pushes whatever it draws from toward an average. So it always takes something useful (a fire on a cold night) and dissipates it into something useless (a tiny bit of heat scattered through the air).

And if there's no good source of heat around, you could always invoke a bit of "life" as well. After all, a living human is much warmer (and much less "average" in many ways) than a corpse…

  • $\begingroup$ Essentially the magic is stealing thermodynamic free energy $\endgroup$
    – Anketam
    May 5, 2018 at 12:19
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    $\begingroup$ This is definitely the most physically realistic (yet creative) answer I have seen here - especially that last bit showing that energy is energy, no matter the source. Another suggestion for this to actually work in magic would be to smooth the gradient across time - create ice (low energy) now, there will be fire (high energy) there in the future, and vice versa. Magic could be described as being drawn from a plane with 4 spatial dimensions, so it can act across time in our 3d universe. $\endgroup$
    – Blapor
    May 5, 2018 at 15:13
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    $\begingroup$ It also works nicely if you do not talk about heat but talk about entropy transfer. Entropy is the scarce resource that keeps life and civilizations going. $\endgroup$
    – schlenk
    May 6, 2018 at 11:16
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    $\begingroup$ Following @Anketam, I'd go further as to state (either implicitly or explicitly) that usage of magic speeds the increase of entropy in the universe. This would have the ominous effect that magic powerful enough could cause the heat death of the universe or at least bring it on sooner, thus literally taking away the future in some sense: By taking heat from the future to do more work now, less is possible in the future. $\endgroup$ May 7, 2018 at 2:17

Heat is the most traceable, and believable.

The Second Law of Thermodynamics states that entropy in a complete system always increases over time. Heat is a form of entropy already - in fact everything we do increases heat generally around us (even cooling something, we tend to have to make something hotter to cool something down).

So this is already happening now, and it is easy to comprehend to an action today, leading to heat tomorrow, as a primary cost of your action.

Furthermore it is traceable. Already, the cost of our civilisation is generating heat, it would be possible to analyse and model the state of an area and work backwards from this analysis (much like Climate Science now).

Arthur C Clarke said "Any sufficiently advanced technology is indistinguishable from magic." In your case, actually your magic translates easily to technology and our age of convenience, if heat is the ultimate price we pay - we are paying this price today for the 'magic' of our past already.

  • 1
    $\begingroup$ Although making things hotter is actually adding energy via the laws of physics, it allows for easier tracing. Scorch marks persist longer than frost or ice. And, this is magic we're talking about. $\endgroup$
    – Andon
    May 5, 2018 at 1:45
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    $\begingroup$ @Andon Ah, but if you trade heat for something else you get what happens in The Eyes of Kid Midas: everything goes cold and lifeless, and would eventually bring the universe to absolute zero. Or in a more general sense: you'd accelerate the heat-death of the universe. Mind, it would take a lot of heat to do anything useful. But you would be adding entropy to the system. $\endgroup$ May 5, 2018 at 4:11

You want to sling spells like Glarnak and the rest of em cowboy? Well this lifestyle... it really ages you...

You definitely want to drain the life force of the caster on this one. If you do heat or luck, you can run into the problem of always prolonging the cost ad infinitum(cold + luck spells). The cost to perform magic should be based on the strength of the life force of a caster. The more magic used, the more the caster is aged. Incredibly strong magic users would age slower per spell cast. You could even have it so that a spellcaster could burn through all his/her life force to increase the power of another spellcaster . Like a form of magic inheritance from parent to child.

How the choice would reflect resistance as more energy or power is drawn for a spell.

Energy required (whether kinetic, heat, whatever) * spell caster level (golf rules apply here the lower the value the better you are at casting ) = seconds/minutes/years/decades of your VERY LIFE.

How the choice would create a measurable or predictable consequence turning people against magic.

Obviously you don't want to turn to dust and turbo age yourself via spamming fireballs every 5 seconds. This system should make magic cost you and stop you from needlessly casting spells. You aren't going to use magic to pull weeds when you can literally SAVE yourself the time by not casting.

How the choice would be deterministic, meaning the aforementioned consequence could be traced back to a specific action.

Your magic can't rob UNWILLING life. when your magic caster is casting a spell, he/she needs to draw from there own years OR have someone use magic to transfer lifetime/magic capability. Also you can't dip into years you don't have access to. In the same way your muscles give out, if you start to lift a building of osmium, there will come a point where you age away and drop the building.

  • $\begingroup$ This is what I prefer, also, but I'm finding it difficult to come up with a game mechanic that makes this interesting. In any case, I would always have the effect on the caster. $\endgroup$
    – NomadMaker
    May 5, 2018 at 7:22
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    $\begingroup$ @NomadMaker I would not use this for a game mechanic unless you wildly jacked up the ability to gain and lose years for higher level heroes. I thought this was more for a story. If you are playing a game... DEF GO WITH LUCK MY DUDE! you have wonderful dice that you can use in conjunction with, rerolls , force your pcs to not roll higher than a certain number when they exhaust luck etc. the possibilities are endless. $\endgroup$
    – Crettig
    May 5, 2018 at 7:31
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    $\begingroup$ When I hear somebody saying they are making a magic system, I immediately think of gaming. Just my experience as a gamer and worldbuilder. If I used life, I would not allow them to recover those years, at least not without a huge quest or something. But yes, Luck is much easier to define. $\endgroup$
    – NomadMaker
    May 5, 2018 at 7:44
  • $\begingroup$ I remember reading a series of books that used a similar system - casting magic temporarily weakened/aged the caster. Cast something big and you'd be a very old invalid until you recovered over several weeks. Overdo it and you'd be dead of old age. $\endgroup$
    – JerryTheC
    May 6, 2018 at 17:42

It can only be luck.

The reason is that clever players will find ways to bend the rules so that the "price" they are supposed to pay is actually a second payday. So they get the spell they want and also a nice, free campfire in the evening.

Luck is the one thing that behaves non-deterministic and thus can be used by the GM as a tool instead of being abused by players.

  • $\begingroup$ Upvoted! I regret that I can't select this as the answer. I set the rules, and "believability" was the condition. Dang. Heat is more believable - but you've made a whomping good point that I'm not going to ignore. $\endgroup$
    – JBH
    Jul 16, 2018 at 4:10

Not quite luck, but organization

Instead of having a system were using magic creates a penalty in the form of random bad luck try a system that penalizes by randomly destroying organization similar to what was created in the future.

Just about any use of magic could be seen as organizing something, for example light a flame and you have organized heat, build a structure and you have organized materials, stop time and you have organized time. The consequences can then follow with results that come back to what created them. The cost of a fire is that heat disperses sometime in the future, someone feels a chill or fire goes out. The cost of a structure is that other structures (or even the created structure sometime in the future) are liable to suddenly collapse. Stop time... well get ready for some paradoxes suddenly occurring in the area.

This system makes it very easy for the effect to be traced back to the cause and can definitely turn people against magic based on a net neutral or net loss effect. A mage might stop a building full of people from collapsing, but would they really be hailed as a hero if the people know that another building will randomly collapse on them in the future?

The same way many of the heat responses point to entropy, this too would be an entropy inducing event. Entropy is the tendency to move from organization to disorganization. The energy of an object moving in a certain direction is more organized than that object at rest with the energy converted to extra heat. Two objects at different temperatures is more organized than the same two objects with their temperatures averaged.


In my opinion you could simply have "schools of magic", that teach the manipulation of different types of energy (life, luck, heat, motion...) For example, if your mage wants to move a huge rock in one direction, some thing (or innocent passer by) in the future gets launched in the other direction with equal energy. Or if you want to light your fire with magic in a cold winter night, the spot could freeze over the next day.

Why everyone hates necromancers? To reanimate a corpse in the present, life-force from the future have to be drawn in, killing someone in the process.

I would post this as a comment rather than an answer if I had the reputation to do so, as it is not a direct answer to the question.

  • $\begingroup$ That sounds kind of like the Death Gate Cycle, except the time element. Magic race figures out necromancy, doesn't realize until far too late that every time they animate a corpse it steals life energy from one of the members of their race currently in suspended animation waiting for their great work to be completed. $\endgroup$
    – Marbrand
    Jul 19, 2018 at 10:36

I would either use Life or Luck. In all cases, however, I would have the cost paid by the spell caster.

This would prevent most casters from just throwing spell after spell, because the cost could be extreme.

In the case of Life, which is my preference, the caster would age much faster than expected if he cast too many spells or too powerful of a spell. This would probably have the effect of having fewer casters because most people would say, "no way" to dying of old age in their twenties.

People tend to remember the extremes rather than the averages. For example if a few times you go up elevators it takes a long time, most people will remember that rather than the much shorter average time.

There is a long history in fantasy of magic being paid for by life, though usually it is the life of a deliberate sacrifice. I'd allow that, as long as it is a sentient being and the sacrifice is painful to show that it is an evil act and to discourage players from using this.

My only problem is that I can't think of a game mechanic to make this a problem for the player character unless he goes to extremes. I've never had a character die of old age in a fantasy game. Either the campaign ended within 5 years game-time, or my character was killed off. The only game where my character died of old age was Traveller, and that was in character generation (yes, it is common to die in character generation in Traveller).

Luck is much easier to define in game terms such that the player will understand that it is a real problem.

Also, most physical magic could be defined as transferring luck around (altering probability). However, I'd also power them through future luck.

Luck could also influence society more than Life. An unlucky caster in the middle of a town is a danger to everybody.

I think I'm going to use this idea for my next fantasy game.

  • $\begingroup$ My only problem is that I can't think of a game mechanic to make this a problem for the player character unless he goes to extremes. well, there is the concept of "cast from HP". In essence, any magic will "damage" you in some way. This can range from directly paying the casting cost with life (think spending HP instead of mana) or somehow indirectly doing it (say, you sustain up to 5% of your life as damage per casting, alternatively you can only restore MP by causing damage). You can also extend that, so magic may lead to suffering a disease or just pain (reducing effectiveness), etc. $\endgroup$ May 6, 2018 at 18:31
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    $\begingroup$ There is also the Mage: the Ascension and Mage: the Awakening RPGs by White Wolf. In those casting overt spells will lead to getting Paradox. It can and most likely will cause a magickal backfire at some point. It may be right when you cast the spell or later on when you've cast a few and you have some more Paradox hanging on you. This can lead to a simple backlash which just harms the mage, to the mage becoming "odd" for a while (milk curdles around them) through to the effect of the spell being warped, to the very reality warping itself and lashing at the spellcaster in a bizarre way. $\endgroup$ May 6, 2018 at 18:38

Heat would be the most believable. Heat is a type of energy transfer in which energy flows from a warmer substance or object to a colder one, which means that it's just another form of energy.

So, these are some other forms of heat that your magic can use as its energy source:

  • The total calories stored in the caster's body from the future, from the time the caster casts the spell to the time the caster dies. For example, a caster is 20, and is going to die at 60. Let's say the caster gains 2000 kcal per day. When he/she casts spell that costs 100.000 kcal, that energy requirement is shared equally to the remaining days of the caster's life. So, each day he/she is going to lose 0.007 kcal/day *. The consequence is the caster gets hungrier and hungrier as he/she casts more and more spells. This creates a measurable or predictable consequence turning people against magic. As the caster gets older, the same spell is going to cost more, which creates resistance as more energy or power is drawn for a spell (Although, this gives people incentive to start using magic at early age).

  • Calories can be absorbed from people around him/her. However, you need to come up with arbitrary mechanism to determine the speed at which the energy is drawn. My best suggestions are:

    • To base it on distance and difference in "pressure" between the caster and the object in which the desired energy is located.
    • To make the caster have some sort of gravitational pull.
  • Matters around the caster. E = mc^2. Energy is matter, and heat is energy. Matters around the caster simply disappear bit by bit, or get absorbed by the caster. Basically, the caster becomes reverse radioactive, causing cancer in people around him, forcing him/her to go into exile. Or you can make the caster to be the one who gets the cancer. Calculating energy in matter and radiation is not that simple, but you don't have to be able to explain in great detail how it works.

  • You can even only use specific matter or substance, like e.g.

    • Water. The caster gets thirstier as consequence, or the caster creates drought in the village.
    • Chlorophyll. The caster wither plants.
    • Sugar, Calcium, Neuron, or anything that creates sickness from the lack of it.
  • Or you can just use the heat.

Since you are just borrowing energy from the present that you are inevitably going to return in the future, conservation of energy is maintained. So, everything "makes sense". It's also deterministic, meaning the aforementioned consequence could be traced back to a specific action, since this system follows a solid rule. Nothing is random.

* 2.000 kacal/day - ((((60yr - 20yr) * 2.000 kcal/day) - 100.000 kcal) / 60yr - 20yr)


Assuming you still like luck and didn't rule it out for the reasons stated above, my answer would be all three.

Careless beginners draw from the future and don't really know what they're drawing on. Experts learn to tap one of the sources, but the magic it provides has different flavor or limitations than the others. Gurus learn to draw on whatever they need at the time, or a mixture, to produce effects or power levels no one else can match.


Well, take a look at our modern magic of technology. It “pays the price” by drawing its energy from the past.

This affects heat, and through heat also life. Using that magic on a global and pervasive scale will be climate-changing in the long run. Welcome to a new ice age ruled by wizards.


Short answer: Life

Long Answer: You see life powering things is common in fiction and ancient technology, so it would make sense in a non-scientific magical setting (yes I'm assuming but so will you readers). The Spirit/Soul is considered to be the life of a creature in many cultures, religions, and myths, so people will understand this and find this logical, heat and luck aren't really associated with being drained by magic spells. Also a consequence could be the same as (Movie Spoiler Alert - Infinity War)

the end of Infinity War, killing half of the universe

or if you want to be Biblical, one third of the Earth, that would definitely cause people to turn against magic. Now think of this you can trace it back by looking at who died, the family lines of those who used the magic spells, the more powerful the spells they used the more of the people in the family lines that die. This may not get as a many as a third of the population of Earth (not sure how common Wizards are) but it will likely be at least noticeable.

  • $\begingroup$ Would you mind editing your answer so that the name of the movie appears outside the spoiler tag? That way the reader is more informed about whether they should avoid reading it. $\endgroup$
    – jsm
    May 10, 2018 at 15:16

Life, with a certain catch: the wizard casting this spell has to select someone or something alive to gradually drain its vitality. Think of this as a form of magical mortgage, with the wizard having to pay his debts in a timely manner, unless he wants the missing vital energy to be drawn from himself (rare, but not unheard of).

Energy can be drained from basically all living things, including plants. It is extracted continously over time, i.e. the wizard has to concentrate on draining for months if needed. The health of the victim gradually worsens until they die. The energy which can be drained until death depends on the intelligence and general health of the victim's mind and body - i.e. humans give the most, but a pack of dogs might replace a human, and even destroying a large field of mature crops might also power some magic.

However, this side effect should not be used as a weapon or herbicide spell.

1) The higher the self-awareness, the easier it is for the creatures to notice an intrusion into their minds - thoughts which are definitely not theirs. It proves surprisingly hard to extract from a creature who's simply aware of your presence and angry at you - which is why even uneducated peasants can repel your invasion if you don't exercise caution.

2) All creatures have some natural mental resistance which is always present. It becomes challenging to overcome when you have to break into many minds simultaneously - and you often have to do this. Wizards pay off their debts as quickly as possible. The entity from which the energy is borrowed is not a patient one. If it's not satisfied with the backflow of energy, it drains the wizard, and if the wizard runs out and dies, he's not relieved of his debt. For a single powerful spell you might have to kill off entire villages at once - full of people who will try to coordinate themselves and resist you. The natural resistance doesn't really depend on intellect - which is why draining life energy from a field of potatoes is much harder than it sounds.

3) A bond being formed is easily detectable for someone with a bit of magical knowledge. You are particularly vulnerable when using it. That's why this is never used as a means of assassination.

In short:

Are powerful spells harder? Sure. You have to fool more donors, which is like the difference between playing chess on a single board versus many boards. Not to mention the ever-increasing risk due to 3).

Does it turn people against magic? Absolutely. Generally, mages do unpopular things which end up saving more lives than they take (i.e. stop a battle or create a river in a desert), but sometimes it's just some fireworks for a royal birthday.

Can it be traced to a wizard? Yes and no. It's hard to determine whether a specific illness or blight is magical or not, but if you saw a distant white flash, and then your sheep started falling dead, you probably know who did it.

  • $\begingroup$ Hello, DrunkenSailor, and welcome to Worldbuilding.SE! Please take our tour and visit the help center to learn more about the way the site works! $\endgroup$
    – Gryphon
    Jul 22, 2018 at 21:49

In a magical system, each being has a relatively conscious energetic field far greater than their body's physical space and time. In effect they are a self-directed node, in a self-aware universe. Strength and consciousness are relative to the person's degree of magical ability, whether innate or gained through practice.

Mages, at the minimum, have an extended awareness akin to the nerve endings in a fingertip. They exist in a web of reverberating actions and reactions. Like a spider, they know a step here will send reverberations / exact a cost, there, there, and there. Star Trek had 3-dimensional chess. This is a 4-dimensional (3-d + time) spiderweb. Training could involve ethics. Otherwise young or unstable mages would wreak havoc in their learning stages.

Generally, any person's field overlaps with others' to a degree, spanning space and time -- present, future, and past. A stray effect of a past magical act can give an unexpected shove to a current magical act, for better or ill. That's part of where luck comes in -- it could be a wild card. Sudden cold could save your life in a heat wave. Your enemy could have a drop in life force. For whatever reason, the effects of magic are weaker or less predictable on past reality. Maybe because we tend to be aimed toward the future, and the collective consciousness is a powerful force.

The effects of a magical act do rebound through space time like billiard balls, with distance based on strength, and vector based on physical location, and a personal relationship factor -- family, organization, tribal affiliation, friend or foe. Life, heat, and luck play into the effects based on the intent and emotions behind the magic, but it's not predictable and there is overlap. Luck may be affected by strong interconnected strands of magical deeds, that strengthen the fundamental connections between people or groups, and help line up structure and "chance" events. One man's luck is another man's downfall.

Resistance: the more complex or thickened an area of space time, the more a spell might bounce off. This would affect both the spell and the side effects. The spell would appear weaker due to dissipation, as the power actually fragmented off into multiple directions, so a mage would have to exert more effort.

Robert Holdstock's Celtika has a very long-lived Merlin character who spends his magic ability very carefully, because each expenditure ages him relative to the amount of magic used. He literally loses life (and in your scenario would potentially lose heat and luck) with each magical move).


If you want to invent your own custom laws of nature, any of them can make sense. You just have to invent a set of universe with coherent laws of nature in which "life energy" or "luck" is a real, quantifiable thing. If you do this, decide on some rules that make sense and stick to them strictly. I'll write the rest of my answer assuming you mean which of the three makes the most sense assuming the laws of nature as we know them, i.e. which makes sense to someone living in the real world.

1) It makes the most sense to expand heat to be energy in general, as the word is used in physics (i.e. not "life" or "luck"). Allow the energy to be drawn by means of a link to the future which is attached to a specific object, whether that object be internal or external to the caster's organism, manufactured or naturally occurring. Then when energy is channeled, let that energy be taken from the source that has the highest net potential energy in the immediate vicinity of the future version of the linked object. If at that future time the link is immersed in heat or light, there will be a transition to cold or dark. If the place is already cold and dark, then the binding energy in matter can be used and future objects disintegrate.

The caster can't choose the time from which he draws, but the distribution of times can favor certain time frames. In other words, occasionally the time frame could be a few seconds or a few millennia, but in general it is a few years or however long you as the creator want. In the event that you want to explain this randomness, you can give some hand-wavy pseudo-scientific explanation based on over-simplified quantum mechanics.

Because the effect would always take place in the vicinity of the linked object, and assuming that the caster would want to always have his amulet/wand/whatever on hand, the effects would always affect the caster's future, sometimes to the point of damaging his body or possessions.

2) If you wanted to assume some kind of non-local hidden variable interpretation of quantum you could do luck as a manipulation of these hidden variables to affect probability. Then magic is just manipulating probabilities of microscopic natural events to get your desired event, however unlikely, to become the most likely outcome of a situation.

This could require your mages to be intellectual in order to understand the inner workings of the thing they want to affect. It would also require greater focus and mental power to process the probabilities involved in larger/complex spells.

If you want this to be linked to the future, you could say that this adjustment of probability makes it harder for less likely things to happen in the future, amounting to a drop in future luck (or an increase if you are trying to avoid an unlikely death). This would be believable enough for me if explained in terms of quantum effects, but I would still prefer the previous solution.

3) Lastly, if you really really wanted to do life, you could justify it by saying that your original mages created a "machine" that communicates with the mages and translates their commands to physical effects in the world but takes from them physical health. Then when they cast a spell they are actually communicating their desires to this "machine" which then accesses their part of the world from a distance and causes the desired effect. To me this would be believable enough but would sound silly, and I would be left wondering who the sadists were that thought that life would be a good currency for magic. It would also allow for mages who study the machine instead of studying spell casting to "hack" the machine and do whatever the heck they want, defeating your purpose in making magic consume life-force. Basically, the consumption of life would not be fundamental to magic.


You should drain heat from the future, turning it into a frozen hellscape

You should drain heat from the future, instead of generating it in the future

The concept goes like this:

Your magician's keep drawing energy from the future, which slowly and permanently turns the future into an increasingly inhospitable ice world/frozen hellscape. As the world slowly turns into a wasteland because all the heat from the future has been drained, you create an increasingly bleak dystopian setting for the survivors.

The worst part is that by the time the people in the future encounter the effects, there is nothing they can do about it.

The sites of past great magic can be places that are incredibly cold and sap the heat from the environment for miles. As people keep casting in the same locations, for example in cities, those places become increasing cold and unlivable forcing people to move and make new cities. Locations where magic has been cast over and over excessively can reach absolute zero in the future; freezing to death anything that enters its vicinity instantly.

After some time there is just not enough heat on the planet to sustain life. The places were magic was cast in the past are like black holes for the heat on your planet. Crops die from frost, people die from cold, and eventually life is unsustainable. Those are the stakes; Death for all.

Thematic Tie Ins:

You may notice that this story becomes a lot like the story of global warming. You can draw some thematic similarities to this. The people who enjoyed the benefits and lack of consequences in the past leave the world devastated for the people in the future.

By the time of your story you can be somewhere between the golden age of magic, and the death of all that lives from cold. So in world stuck in permanent fall/early winter, there can be great attempts to limit the use of unnecessary magic and the further destruction of the world. The magic users who disregard the consequences and practice how they please can be under heavy scrutiny by the law, or even be criminals.

Seems like a cool setting to me.


There is already a chosen answer to this question (which is awesome). I'd like to suggest a different avenue that could well fit into many tropes about wizards in general and also have an in game impact.

Life is your form of resistance. Here is how I would make it work.

Every spell is accompanied by a brief premonition of the spell caster's death. This premonition is the most likely death of the spell caster if he leaves magic alone. It IS subject to random events, but that death is the most likely and has about an 80% to 90% chance of coming to pass. Most of the time the fledgling spell caster will see himself as an old man surrounded by grand kids.

Each successive spell moves the timeline up and the violence of the death up a notch. The fledgling spell caster might notice that instead of passing quietly, he has a heart attack as an old man, with one fewer grandchild. A wizard that focuses on generally beneficial magic will experience less increase on the violence. One who chucks Fireballs and Lightning around ups the potential level of violence.

The time and violence increase with the amount of magic as well. Smalls spells don't have dramatic effects on the premonition, while great workings may take you from a late middle age heart attack to an early middle age death at the hands of an angry mob.

This can have a few effects on how the wizard behaves. Ever notice that a lot of old wizards in various works of fantasy seem to be reluctant to use their power? This would explain it. They saw their death change with each spell cast, and they might begin fearing what the next vision will indicate.

A younger mage that has the misfortune of seeing himself dying early might think he's got nothing to lose, and he may become reckless.

Here is an example of progression as the mage learns more and more. He starts out and his first few spells work and the visions show him as a very old man. He keeps going and after a while he begins to notice how much younger he seems to be int the post spell vision after each working, and how much more ugly the death seems. At this point he will begin 'hoarding' his remaining life and magic, and may only trot it out for the most dire circumstance.

Granted, this kind of resistance is not something that is felt or measured, like heat, but it is psychological. It plays into behaviors, where karma for benevolent works might be something sought and those who are reckless and interested in power may not get the idea of the consequence until it's too late.


I'm amazed this hasn't been tackled with physical laws yet.

Luck does not exist. It's simply random chance. Anything which says otherwise is automatically breaking suspension of disbelief for anyone who thinks physical laws exist. More than that, it's bad writing because it always gives you a deus ex machina. Just don't.

Life is less immediately clear, until you realise that old age is merely the culmination of physical processes running out of resources. The same symptoms can happen to young people, and we have a range of diagnoses for these. Old age is an accumulation of all of these things failing though, and death comes when something important finally stops. Since this isn't anything special, we have to reject "life" as an independent concept.

This leaves heat. Conveniently, heat is a measure of work done. That stone you lifted with magic? The energy to do that has to come from somewhere. Not mystic energy either - raw joules in the sense we can physically measure.

  • 1
    $\begingroup$ :-) You know you're answering a question about magic - an intrinsically physical-law-breaking plot device - right? (I'm just teasing, you're making a good point for your argument.) $\endgroup$
    – JBH
    May 6, 2018 at 0:51
  • 1
    $\begingroup$ Sure. :) Well-planned magic systems do have this thought about though. The less you have to suspend disbelief with this kind of thing, the more you can push it in other areas, perhaps? $\endgroup$
    – Graham
    May 6, 2018 at 12:09
  • 1
    $\begingroup$ Anything which says otherwise is automatically breaking suspension of disbelief for anyone who thinks physical laws exist. Uh, what about the Force in Star Wars. It is magic in that it allows you to surpass normal laws of physics. It's also definitely "luck" or perhaps "karma" or "fate" which are all aspects of the same phenomena. I've yet to see somebody cite the Force's aspect of manipulating chance as breaking their suspension of disbelief. $\endgroup$ May 6, 2018 at 18:44
  • $\begingroup$ @vlaz In the original Star Wars, it's supposed to be an energy field encompassing everything. If that's the only level of explanation, then OK, we can accept that. But midichlorians broke suspension of disbelief for nearly everyone. $\endgroup$
    – Graham
    May 6, 2018 at 22:01
  • $\begingroup$ @vlaz And "luck" is very different from "fate" anyway. "Luck" takes place in a random universe - but how would that become non-random for no particular reason? "Fate" though takes place in a deterministic universe. Precognition in Star Wars is only ever related to seeing the consequences of events across that deterministic universe, and the butterfly-effect possibilities - at no point does any character "manipulate chance". Obi-Wan is very clear about that with Han during Luke's training - luck has nothing to do with it. $\endgroup$
    – Graham
    May 6, 2018 at 22:07

One thing you could consider is having the effect in the future be the inverse of the effect in the present.

If the magic makes something hotter, have the future get colder. If it makes something colder, make the future get hotter.

This also gives you more freedom for stories. Having the future effect always be the same doesn't make for interesting surprises.



Heat is well understood and possible to quantify unlike the others. It is possible to establish rules in terms of real-world-physics so that if the author cheats the reader will know. That makes it more believable because the reader gets to use their sense of reason.

Your main rule is the second law of thermodynamics. That is to say every action only serves to spread out heat and cannot concentrate heat from one place to another.

For example you cannot lock onto a 200C bonfire in the future, and snuff it out in return for a 500C fireball to throw the baddies. All you can do is open a portal that allows heat to pass from the future bonfire to the present. You could draw enough heat to start your own bonfire then close it. The result is one big bonfire becoming two smaller ones.

Bonus points if the portal is continuous rather than discrete. That means the heat from the future bonfire is not focused on the present but is spread out along the timeline from now to then. So you can extinguish tomorrow's bonfire in return for a thumbnail sized light that glows for a day. And you can extinguish this evening's bonfire for a torchlight that glows for an hour.

In either case I think the draw of heat should be less efficient based on how far into the future you lock on. This probably means energy is not conserved (lost in the nether space) but this is slightly different from the second law of thermodynamics.

You need to keep the system simple because it will interact with timey-wimey stuff and quickly get out of hand if you want it to be consistent/understandable.


If you're willing to play with the duality of Good and Evil in this setting, I would choose Luck! Consider that the forces of good and evil are omnipresent and balanced, although with slight asymmetries. Sometimes good things happen, sometimes bad. Drawing luck from the future is essentially trading probabilities- to cast a Good Spell now means strengthening the balance towards Evil an equivalent amount somewhere down the line. And vice versa.

Regarding Resistance: The difficulty or resistance felt is the sensation of the timeline adjusting to the imbalance in probability. A small spell merely causes the user or someone nearby to trip and fall; that could happen at any time. A great spell, however, would require a whole host of changes to both the past and future to create the equal opposing effect, providing a strong feedback mechanism to the mage. Perhaps a greater and greater focusing of will while the timeline adjusts itself, until balance is found and suddenly the spell snaps into place.

Regarding Turning People Against Magic: It'd happen quite easily, I think! If healing a broken arm causes another injury, or extinguishing a barn fire causes your animals to escape, the services of magic users would become a hard sell after awhile. You certainly wouldn't want to win a battle using magic if it meant losing another one in the future!

Regarding Determinism: Perhaps not as clear cut as the other options, but rich with potential narrative value. Do the repercussions happen to the caster, the castee, a randomly selected witness, or the location itself? Is the tipping back of the scales always in kind (an injury to pay for each healing) or variable? While it may not have the mathematical order of heat, the balance of luck is fertile grounds for superstition and experimentation.


Combining all 3 together:


Entropy happens naturally and causes the decay, dispersal, and cooling of everything in the universe. When magic taps into its power, it is creating something orderly (as defined by the spell), at the cost of creating disorder in the future. It can cause...

  • Heat to be dispersed
  • Matter to be broken down
  • Life to be damaged
  • Chaos, disorder, etc.

Somewhat related: Mage: The Ascension uses Entropy as one of the spheres of magic.

  • $\begingroup$ Curiously, the MTA link you provided associates entropy more with luck than anything else (aka, randomness or unpredictability). Can you expand on entropy as a solution to the problem? Scientific entropy is simply death (not cooling, though the layman may think so. Cooling against heat creates potential energy. Entropic cooling is literally death, or the loss of all potential). I think there's the seed of a good answer here, but it needs to be fleshed out. $\endgroup$
    – JBH
    May 23, 2020 at 1:10
  • $\begingroup$ One way to think about entropy is "useful" vs. "useless". Since the magic is creating something useful from nothing, the price can be that something useful in the future becomes useless, e.g. plants wither, matter turns to dust, etc. $\endgroup$
    – LukeN
    May 28, 2020 at 19:55

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