TLDR: Portals to other places; wizards use them to make nukes-as-fireballs/anti-personal level attacks, how do they survive?

In a system of magic that functions around opening portals, what considerations do these portals need in order to be “safe” when a wizard casts something like a "fireball"?

The natives have portal magic. They don’t know the magic is based on portals. To them, it looks like a wizard chants a spell and a fireball flies out to smite something. Or they wave their hands and gravity is pulling them a different direction, or some other wizardly spell. Mostly they leave the old guys with the robes and staffs alone because no one wants to be turned into a pile of goop.

The mechanics of the magic system: Some people are psychokinetic in a manner. They can open portals with their brains. Not particularly large portals, and not ones that generally go anywhere useful for travel. These portals are controllable but only the most powerful can make the portal loop back to somewhere useful to go to physically and big enough to pass through. Most of the rest of the ‘spells’ lead to other places that are hostile to 3.5d life, possibly higher or lower dimensions or higher or lower energy state places.

This ability manifests itself in the first person as a talent for thinking in a certain way with a certain pattern, flexing the right ‘mental muscles’ to rip the fabric of space-time apart. Often mnemonic chants and hand gestures are found to help with this when trying to achieve a specific effect. It all ‘looks’ very traditional.

However, when ‘casting fireball’, you create the fireball by ripping two very small holes in a very small space in the fabric of space-time, and colliding different things through them. Your fireball is really a continuous nuclear explosion! This is considered an advanced spell because the portals must intersect in such a way that, when matter exits them both, it intersects and reacts. (The “ball of fire” is thrown by tossing the portal pair at whatever after the reaction is started and sustaining.)

The issue; Our wizard is holding an actively nuking nuke between their hands. How does our wizard survive? Can a small nuclear reaction be small enough to produce the effect of a beach-ball-sized fireball? Is the radiation this throws off survivable? Can it be made survivable with different reactive components?

Edit 1: What is meant by ‘nuclear reaction’? Traditionally, to my understanding, nuclear reactions energetic enough to ignite the air around them are generally achieved by smashing some neutrons into something like plutonium. I know other materials can be used, and some may produce less harmful radiation? The “fireball” part of any spell is literally just a fireball. Atmosphere burning because of the “hot thing” in the middle, in this case a small nuclear reaction. The reaction is continuous because it's being constantly fed new material, but small because its reaction surface is “small.” This might become an issue for the “plane of plutonium” if the explosion propagates through the portal to the rest of the plutonium, but we don’t really care about other dimensions when there are orcs to set on fire.

The basis of the question revolves around the idea that you can react just about anything that WILL react when you mash them together on an atomic level. You don’t have to put the energy into making the basic materials because you're bringing them from somewhere else at a low cost. So technically I suppose, you can “loose” energy as long as the observable effect is a burning ball of don’t-touch-it.

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    $\begingroup$ "Can a small nuclear reaction be small enough to produce the effect of a beach ball sized fireball?" It quite obviously depends on what you mean by "nuclear reaction"; you really need to explain what specific nuclear reaction you have in mind. Some nuclear reactions are even energetically defavorable, meaning that they won't happen without some energy input. And you must explain what "reactive components" means in the context of a nuclear reaction... Remember that a "nuclear explosion" is really just the effect of a lot of heat being released in a very short time in a very small space. $\endgroup$ – AlexP Feb 12 '19 at 14:36
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    $\begingroup$ the only way I understand "portal to nuclear reaction" is if you did something like open a portal to the sun. That has so many of it's own things to worry about. Where are these wizards finding nuclear decay? $\endgroup$ – Andrey Feb 12 '19 at 17:06
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    $\begingroup$ The more I think about it, the more I feel like the coolest weapon would be to open a portal, the smaller the better, miles under the ocean. You could cut through stone, and yet be completely safe if you are not on the business end of it. $\endgroup$ – Andrey Feb 12 '19 at 17:10
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    $\begingroup$ What is 3.5d life? $\endgroup$ – David K Feb 13 '19 at 4:02
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    $\begingroup$ @DavidK Control in length, width, hight, and traveling through one-directionally in time. $\endgroup$ – Marky Feb 13 '19 at 6:42

11 Answers 11


Smite from above.

pillar of fire source

Having a fireball on your lap is hazardous, as is pointed out. Your wizards avoid this. Those who can make fireballs can open portals at some distance. They open them above (or sometimes right below) the target. Some wizards can set it up so the fire comes down unidirectionally, apparently from the sky. It is considered elegant to have the point of origin high enough up that it is not seen by persons on the ground; aiming becomes problematic but therein lies the elegance. A little less art has the fire going up and down equally, looking more of a column of fire than a ball. Those portals can be opened directly above the target.

Wizards who remember certain useful planes with charge difference can open a portal through which electrical charges can equilibrate - a bolt of lightning. Other things can equilibrate through such portals as well; thus the "pillar of salt" technique (the target is actually smashed flat beneath the pillar which emerges from the portal). Some planes contain things more sentient than salt or electrical charge; if you pull something like that into your vicinity (or it comes through) be ready to send it back, or at least somewhere else.

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    $\begingroup$ Nuclear firebalIs are so last century. I prefer the ‘solar energy ten thousand miles from the sun blasting from above through a Fresnel lens of warped space time’ approach. Much classier. $\endgroup$ – Joe Bloggs Feb 12 '19 at 15:35
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    $\begingroup$ @JoeBloggs a Fresnel lens won't do. Conservation of etendue. Unless your Fresnel lens is big or near. Then your foes have a thing to fear. $\endgroup$ – John Dvorak Feb 12 '19 at 18:21
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    $\begingroup$ @JoeBloggs hey, why so far off the sun? why not open the source-portal actually within the sun? the peeps below the destination-portal will learn a new meaning for "sun-bathing" :D $\endgroup$ – quetzalcoatl Feb 12 '19 at 20:00
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    $\begingroup$ Air is not stopping most dangerous radiation. Also, the heat of the fireball driven by nuclear power is even at a few 100 meters instantly killing. Also the sound of the explosin would still be deadly aswell $\endgroup$ – Soan Feb 12 '19 at 20:26
  • $\begingroup$ @quetzalcoatl The answers to this question detail roughly how long you could expect to live if you did that. It is sufficient to say the answer is Not Very Long. $\endgroup$ – Joe Bloggs Feb 12 '19 at 20:36

Why it can't work with nuclear reactions:

What to do instead:

Open a portal to the sun and fling a bit of the material at your enemies preferably from the surface though otherwise it will be too hot for your magician to survive. Also if you take from the core or somewhere near to it you would have the same problems as with nuclear reactions.


  • It doesn't burn the magician when exposed for a short time
  • Its sound is survivable
  • The only radiation occurring is heat radiation
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    $\begingroup$ But... the sun is also a nuclear reaction. $\endgroup$ – Daniel Wagner Feb 13 '19 at 1:21
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    $\begingroup$ @DanielWagner That's why you take from the surface the reaction only takes place at the core of the sun not at the surface. $\endgroup$ – Soan Feb 13 '19 at 6:38
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    $\begingroup$ That's what I thought about when reading the question. Just open a very small portal for a very small window of time in front of the Sun. Change the power of the spell with the distance from the Sun. $\endgroup$ – Echox Feb 13 '19 at 8:21

"Our wizard holding an actively nuking nuke between their hands. How does our wizard survive?"

He doesn't. Not as described. Nuclear is a rather slow way to die in most circumstances. If you have enough radiation to create a fireball, even a small one, everyone in line of sight is going to die of radiation poisoning within a few days.

Lead bunkers will help some, directional casting will help some. But thats 1) not going to look like Gandalf 2) only going to let you cast 1 maybe 2 high gamma spells in your entire lifetime.

Your far better off opening a micro portal to the elemental plane of pure oxygen. At several hundred PSI and similar temperature, you will end up with a nice fireball that will burn just about anything and no radiation side effects. @boomchuck 's water and an alkali metal would also give you a nice portal based fireball.

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    $\begingroup$ A variant would use the old Earth/Air/Fire/Water system. You have to create the right interaction between realms of Air and Fire to create a pillar of fire. (These "elements" are synergistic, so it's relatively the easiest). A true master will get (antagonistic) water and fire working together. Have you seen what a jet of superheated steam can do? $\endgroup$ – nigel222 Feb 13 '19 at 10:09

Low-tech portal wizards would have only one tool capable of containing and directing that much energy: more portals. Either the wizard erects a portal wall to shield themselves and absorb the energy, or perhaps a portal with a spherical surface that surrounds the reaction. In order to see some fiery-ness, that portal would need to be semi-permeable.

Other Notes:

Apart from a spherical enclosure, I don't think a nuclear reaction would produce a ball of fire with a definite shape; it would be more like a point of light, varying in brightness from a dull glowing spot (causes a mild sunburn followed by agonizing radiation poisoning) to a brilliant point of light (face-melting destruction that turns everything in line-of-sight to ash and cinders). If the nuclear reaction is actually occurring across your entire beachball-sized area, everything is vaporized and the earth turns to exploding lava.

I agree with the other answers that a collimated beam would be safest, though the danger would still be incredible.

If your wizards will use this regularly and they don't want to cause cataclysmic destruction, a chemical reaction is probably more suited. They could use portals blasting water and an alkali metal (e.g. lithium, potassium), hydrogen and oxygen, etc.

I'd say, save the nukerball spell for the one-time ultimate climax showdown.

P.S. But for the enterprising wizard who really needs to get things done, a matter-antimatter reaction is the way to go. You get >100 times the bang for your mass transfer buck, and antimatter universes are probably easier to find than Plutonium Playland. That wizard might want to seek shelter in another dimension, though.

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    $\begingroup$ I love the idea of using an anti-matter universe for this purpose. In fact, physicists have recently suggested that our universe has an anti-matter companion on the other side of the big bang. physicsworld.com/a/… $\endgroup$ – Arkenstein XII Feb 12 '19 at 23:16

This question seems to be stemming from the notion that the ideal way to create a "fireball" is through a semi-controlled nuclear explosion. However, given the way you have established magic to work by way of portals, there are likely plenty of other ways to create a fireball-like effect using much more mundane means.

(A lot of stuff in this list would require precautionary measures in their own right, but I'd think they wouldn't be nearly as complex as what a nuclear explosion would necessitate.)

Any Liquid/Gas Hydrocarbon Fuel

There are an incredible number of -anes and -anols that are splendidly flammable. Use a liquid form if you want the flame to spread and linger or a gas form if you want the flame to be explosive and dramatic.


While not overly destructive on its own, burning magnesium can result in extremely high localized temperatures and also has the effect of burning so brightly that it can result in blindness.


On a similar thread as Magnesium, thermite burns so hot that it can easily melt through most modern substances and just about any primitive ones. It also has the benefit of being unable to be extinguished by water.


Simply the mixture of a gelling agent and a flammable liquid (like gasoline/petrol), this stuff will burn hot and long while also being rather sticky. (This stuff actually is banned from use in warfare as part of the Geneva Convention - that's how effective it is.)

Chlorine Trifluoride

No list of flammable things would be complete without good old ClF3. This stuff is so nasty that it doesn't even need an ignition source to spontaneously combust. It's a good thing that it's being summoned via portal - this stuff is so volatile, it has a decent chance of blowing up in your face even when it's being handled properly.

Other Things

This is just a list that I came up with off the top of my head and is in no way exhaustive. The pure oxygen approach mentioned in another answer would be just as practical. And I'm sure any number of chemists could jump in and add their own incendiary concoction to the list.

And hey, we're working with a portal that can bring things in from other dimensions entirely, so what's to say that in one of them there's a special element that burns at the temperature of the surface of the sun but holds its shape long enough to physically throw? Or perhaps you can source your fireball from a dimension that is nothing but super-heated plasma?

Maybe there's a dimension that has sentient fire, even... though I'm not sure I want to consider those implications.

  • $\begingroup$ I like the path your walking down, and for the story something like this would probably more appropriate then the initial premise, but I cant otherwise go for an answer like; it's answering a different question then was asked. $\endgroup$ – Marky Feb 13 '19 at 6:46

Two options that I can think of:

Lead-lined robes : Unpractical, probably too heavy and hot for comfort, but that should do it for some apprentice practicing in their master's lab. Don't forget to wear the fully protective lead-lined conic hat that comes with it.

Cast unidirectionnaly before you : One of the most basic way to prevent radiation to propagate in nuclear facilities is to have angled corridors. It goes in a straight line with a "U" shape in the middle, the center of the "U" being a BigFatBlockOfConcrete™. Radiation travel in a straight line. So as long as you create the opening in front of you, the radiations escaping from the portal goes straight in front of you too. (The resulting radioactivity in your environnment and of whatever comes out is still dangerous though.)

Remind your casters to gulp down their iodine solution every once in a while and to get as far away from magical battleground as they can once they're done.

Also, the Magical Workers Union is pushing for a maximum mSv annual threshold beyond which your ruler is forbidden to ask you to cast any more nuclear spell.

  • $\begingroup$ a 1 foot by 2 foot lead plate thick enough to reduce your gamma exposure by 50% will weigh about 50 pounds, so "too heavy" is a pretty hefty understatement. google "halving thickness" if you want to check out other materials. $\endgroup$ – Corbin Matheson Feb 12 '19 at 16:18
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    $\begingroup$ Well, 50% of how much? Depends of the amount of radiation escaping of a fictionnal portal leading to a fictionnal plane of existence. I was just pointing out that protective clothes would be the first measure. Lead is the main example of "insulator"(?) and easily available almost everywhere. If you can't train with a protective gear, switch to confinment. You just don't want to tilt your head too far with your wizard lead hat, lest you'd break your neck. $\endgroup$ – Nyakouai Feb 12 '19 at 16:24
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    $\begingroup$ Its kinda like sunglasses for gamma rays. If I have sunglasses that block 50% of light, that means that if I have 10 watts shining on one side, 5 watts get though, if I have 100 watts on one side, 50 watts get through. This holds true right up until your sunglasses melt. Same thing for your lead plate. $\endgroup$ – Corbin Matheson Feb 12 '19 at 16:57

Perhaps the wizard can survive if the material coming out of the portal is moving at very high speed away from them. If it's at a sufficiently high fraction of the speed of light, any radiation coming back towards them will be Doppler shifted down to safety. Such material could be obtained from astronomical sources (maybe hot hydrogen gas orbiting near a black hole)?

I am reminded of The Witling, a novel that has a very similar magic system, in which people summon strong winds from the other side of the planet, where even the atmosphere is moving very fast relative to the wizard.


Warp space directly around the output portal so it all points at the target. Radiation transiting the portal radiates in all directions, but as part of the localized severe distortion of the space continuum which the magic caused in order to create the portal, all directions in space around the portal actually temporarily lead in the direction of the target. This puts the magician "behind" all of the omnidirectional radiation.

Magicians may refer to this as "focusing" and the precision and shape of the "cone" of where the warped portal space points can vary depending on some factors.

Note there may be secondary emission issues which could still impact the caster. Hopefully these will be far smaller in magnitude and can be dealt with in more mundane ways.


How about nuclear Fusion? It's still a "nuclear reaction", but it avoids the messy consequences that plague the Fission reactions that most other answers seem to favor.

No radioactive waste of any serious consequence.

Definitely hot enough to qualify as "a burning ball of don’t-touch-it." (I love that description, by the way).

Assuming fine control of portal size, and assuming cooperation of the materials on the "other places that are hostile to 3.5d life" sides of the portals, it could be regulated down to single atom collisions at a time (might look something like glitter) up to giving birth to a full blown star (limit the effect as needed by placing a maximum size on the portal to those particular "hostile places", or limit by the lack-of-death wish of the portal creator)

As long as the caster is careful, heat is the only serious concern.


I love this idea for a weapon.

However instead of this: "Most of the rest of the ‘spells’ lead to other places that are hostile to 3.5d life, possibly higher or lower dimensions or higher or lower energy state places."

What if the small portals lead to places above a center of gravity that has a lot of matter being compressed towards the center of gravity. Places like the bottom of the ocean (water) or just above the center of the earth (lava) or just above the center of Jupiter (metallic hydrogen) or just above the center of the sun (plasma). The further the distance the more powerful you must be. Maybe you are very powerful and you can make a portal inside a neutron star or black hole.

The matter and energy coming out of your nearby portal will be very directional. In the case of a star portal maybe fusion isn't happening after the plasma leaves the portal because its not compressed. It will expand rapidly though so maybe small portals.

If I were going to shoot black hole matter I would make sure I was redirecting the expanding matter and radiation away from me using a second portal and/or jumping into another portal to get out of there fast.


Simple! Just put a few extra portals around the rest of the explosion, leaving only one side open. All of the heat and light on that side will be fired like a cannon, while the other sides would be shielded. However, there'd better be a nice empty place for the explosion to go, or somewhere else will receive the full blast.

This might look more like a laser pulse than a fireball, but if all sides were surrounded and then one side of the portal were quickly removed and then replaced, a small burst of energy could act as a "fireball"


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