Ley Lines are straight alignments crisscrossing the planet from east to west. These lines contain sources of magical power called mana, and coalesce at various locations around the world. This allows for the use of magic in the world to produce spells, but has also given rise to technology that has revolutionized society. A magical version of the internet allows the world to be interconnected through the use of crystal balls. Using these balls, one can communicate to another individual thousands of miles away. They are activated with the user's mana, which sends a signal carried through the ley lines to the recipient. The ball on the other end alerts the person to the attempted communication, and activates it on their end to form a connection.

However, there are problems with the system, specifically in areas where the ley lines meet. A magical "dead zone" forms in the locations where the lines coalesce which prevent signals from passing through, preventing a connection from being formed. This leads to a buffering that kills the link between two parties. These dead zones also cause issues with other forms of magic. Mages find it more difficult or even impossible to perform their own spells in these areas, despite there being a large concentration of mana in the area. This seems counter-intuitive, as this overabundance of magical potential should lead to an increase in magical ability and boost signal bandwidth.

How can this be rationally justified?

  • $\begingroup$ Possibly see Yuuki Tabata’s Black Clover. The series has a concept similar to this where areas with very high natural concentrations of magic (called 'high mana zones' in the series) are very difficult to use magic in because all the 'background' radiation interferes with a mage’s ability to form their own mana into spells (aside from being dangerous for other reasons). $\endgroup$ Oct 11, 2020 at 18:44

11 Answers 11


Mana, like radioactivity, is harmless in small quantites but causes problems in large concentrations.

At extreme "ambient mana density" levels like those you'd find at ley line intersection points, the "spell matricies" of high-complexity magical artifacts like your crystal balls begin having problems and signals that pass through them are disrupted. This is similar to how computer chips and radio signals behave in high-radiation enviorments, where individual particles can flip bits inside of the processors or messages and cause all sorts of unforseen software problems. Similarly, Mages have difficulty casting complex spells because they can't stabilize their spell formula/matrix/pattern without it being disturbed by ambient mana particles before they're done casting.

This can have some neat knock-on effects, for example:

  • Since Mages can't cast complex spells in these dead-zones, they need to "go back to basics" if they're inside a "dead zone". Only the most simple cantrips are castable--anything more complex gets destabilized too quickly--but these elemetary spells can be cast with incredible force due to the high ambient mana density

  • These dead-zones can also be the cause of naturally forming magical monsters. Similar to radiation, creatures that live inside a dead zone have a high chance to produce mutated offspring, who, if they survive, have a high chance of being able to innately manipulate mana and perform rudimentary sorcery (like body enhancment or fire-breath or whatever)

  • Similar to how computers that are built for space travel are "hardened" against radiation, magical devices could be "hardened" against high mana density in the form of redundant magical circuits, self-repair functionality, shielding, etc. These would be significantly more expensive than regular magical devices


Mana, like electricity, does no good just sitting around. It is the flow of electrons that brings about the light in your electronic lamp and all the other electronic devices that you rejoice in. What is needed is a differential so that mana will move.

A place just jam-packed with mana has no place for it to move -- the areas outside being the equivalent of electronic insulation. Any meeting point of ley lines that was not surrounded by mana insulation rapidly ceased to be one by loss of mana; only the insulated ones remain.


Yellow And Blue Make Green:

But what happens when a wizard can use yellow OR blue, but green is nonsensical? Different ley lines have different wavelengths. This is why there ARE ley lines (like wavelengths attract), and not a diffuse mana field. All of it is Mana, but the mana has a different feel based on wavelength or "color." Mages generally are only able to process a single wavelength of mana at a time, but can perceive many (which is why mages can go to other ley lines and use the mana). However, where these colors blend together, the perception of the color changes, such that the apparent color is different than the individual colors.

Initializing a spell takes careful consideration of the wavelength. Try to take a white wall with yellow dots, and then flood the room with yellow light. Now put your hands on two of the yellow dots on the wall. Good luck. If you saw them before the yellow light went on, you might have a chance. Otherwise, all the light reflected from the wall looks yellow. This is what it's like trying to use mana in a place flooded with different wavelengths of mana. You can use one color, but when multiple colors are blended together, it's hard to pick out just one. Using the wrong wavelength in casting is unstable at best, dangerous at worst.

For your crystal balls, the problem comes in that the messages are sent along a single wavelength. The mage must magically perceive the wavelength or color along the whole distance. When the intersection is met, the colors go rampant and blend, making it difficult to distinguish one color from another. The connection is lost unless they are really lucky or if they have a special disability.

If you like, you can have some individuals who are essentially "colorblind" to certain wavelengths. Envision someone who is unable to see a certain color of mana. These poor souls will be unable to use certain ley lines at all, because they lack the perception to see that mana. But these people would be lucky enough to be able to use mana within the intersections of lines they only see one color of. The reason? They can distinguish the color they can see from the one they can't. If you allow the spells to USE all the mana, but the INITIATION of the spell requires a single wavelength, then these otherwise "disabled" mages suddenly have a distinctive and powerful gift. If not, then they just have the neat trick of using magic within an intersection - and transmitting through intersections other can't.

Perhaps these folks can detect signals sent into the intersection. These mages could then initiate a second signal starting from their crystal ball. It could only be sent along one of the two colored lay lines, but it would allow transmission of some messages via a network of colorblind mages - a sort of telegraph station system. There are interesting strategic implications for this in a world in need of long-range communication.

A unique application of this comes if you wish to imprison mages. Build a prison for mages within an intersection, but staff it with guards who are "colorblind." While the general mages struggle to start spells at all, the guards easily smack down prisoners at the first sign of trying.


Too much.

dog urine grass


Dog urine has nitrogen that plants need. Too much "burns" or overwhelms the plant. You can see that surrounding the dead patch the grass is healthier and brighter green that lawn more distant. It has more nitrogen but not too much.

So too the mana concentrations. It is too much at the intersection. It is not so much that magic does not work there, but more a "drinking from the firehose" principle. The firehose has good water but is liable to take your lips off if you try to drink from it.

Just as grass grows green some distance from dog pee epicenter, at points some short distance from the actual intersection one can take advantage of power bleeding from the intersection into the lines, and magic could be more powerful there.


This is exactly the same issue the Internet had before switches effectively replaced hubs.

In computer networks, there are two basic types of hardware that converges multiple lines to allow computers on a network to connect to each other.

  1. When hub receives some incoming data, it will forward it to all connected computers. This means the more computers there are connected to one hub, the less overall bandwith each of them has. In older networks, where data can only be transmitted one way at a time, collisions happen all the time (i.e. both ends are trying to trasmit at the same time and neither will receive the message).
    And if you manage to connect hubs in a loop, you can only pray to the Internet gods for mercy (and disconnect them from each other).

  2. Switches are significantly more advanced. They can be programmed to only route traffic for example from input A to output B and from input B to outputs A and D, and discard anything that comes through input C. They used to be more expensive and too hard to use for regular users, so they opted for hubs.

You can view natural Ley Lines crossing as a hub - due to high traffic in the area, the messages will come delayed, may be lost altogether, and trying to send message from hub will generally annoy everyone who tries to use the network at the same time.

These natural crossings may be upgraded to "switches" - it comes with a price and you need a skilled magician as an administrator to program it initially and maintain the proper work, but you get interruption-free communication and much better speed (and maybe, if you are wealthy enough, your own dedicated line to connect to the MagicNet).

  • Magic highways. Think of a very busy and central highway. As long as the cars are all moving without stopping or going from a lane to another or doing anything like that, just a road with cars going in and getting out at certain points. This street has no traffic or problems as even when a cars slows down to go into an exist it is predictable and reasonable. But imagine the same street with two busted cars in the middle and you have a jam. Some magic jams are the problem. This can be caused by a hundred reasons. The mage can be careless and like your own car that needs service they can just cast a half baked spell so it gets in the middle of the magic highway and just stops. Now since you did mention lines I will assume they are limited to actual physical space. So the first idiotic mage that does a good morning spell to his mother on the other side of the world before he is fully awake just sent a spell that got to the middle of the magic highway, sounds like a power metal track, and it stops dead while the rest of the magical world is reduced to a slow crawl until it is solved.
  • Tiny tiny space taking spells. Sounds boring but again lines have space and even if your spells are very very small in size they take space. Imagine how long would it take to full a stadium with matches. But it can be done. And once it is full you can't find that light green match you want to use.
  • Video game bugs. Pretty simple stuff. Spells are like codes and once they start interacting they can just glitch or have a bug. I think most people are familiar with video game bugs but let me give you an example. If an NPC is supposed to be programmed to go to their house at 11 P.M to sleep, but their house door is blocked by a giant boulder or a skeleton of an enemy then they might be in a problem. There are too many factors to consider but basically you have an overall conflict because it is coded to preform this task but the engine also limits the NPC to behaving like actual people so it has to move to the door and get in but it can't move because a boulder is there and so on. So spell might be like that. Maybe the attract or overtime spells think that this other spell is actually it's own. And tries to establish contact and you end up with one mega messed up spell.
  • External factors. Overtime a new type or rocks, fungi, trees...etc evolved in those places and it is highly interactive with magic. Highly interactive does not mean instant jam. It means that it can simply interact and might change the properties of the lines or spells in them. They cane feel on the spells or whatever really. But point is they cause problems.
  • Fail safe. As mysterious as the lines themselves. Or if the line are explained slab it in there as well. Anyway the theory is that at a certain level of magic the line are stable and everything is going well. But if the amount going through exceed this limit then the lines EXPLODE or something.
  • Anti magic lines. Why not! You have magic stuff so maybe there are lines of anti magic that stops or disrupts magic. Perhaps you can have that be dark magic or blood magic lines and because of the secretive nature of the magic, because it is evil duh, only few wizards know about this thing.
  • Week points. This is more about engineering but maybe magical engineering or whatever you feel like. Basically those are week points by nature. Like the knee joint on human or a window on a spaceship or something similar. Just by nature the magical size or actual size of those places is smaller and things get stuck in them more often

Most magic systems have some form of connection to the person's will and intelligence. Spells can often identify friend from foe or heal specific things on a person. I often say that a spell basically "shapes" the raw mana. Like a sculptor you use signs, your voice and your mind to shape the mana into the form you want and off it goes to perform your spell.

This gives a clear way to dispell someones magic: deform their spell in some way to make it burn itself out or become harmless. It also means that large concentrations of mana can interfere with your spell as raw mana attaches itself to your spell. This isnt a big problem for lower concentrations as not enough can attach to it.

This also gives you a nice way for magical items to perform: the item prevents raw mana from interfering with the spell locked inside, and mana pushed through the item is shaped by it into the form you want, causing the spell to happen.

It also gives you a clear reason why some spellcasters can be more powerful without actually having more mana: they are simply superior sculptors of the mana and know tricks to sculpt it better than the "standard" spell.


Mana comes in waves, therefore it is subject to constructive and destructive interference:

In physics, interference is a phenomenon in which two waves superpose to form a resultant wave of greater, lower, or the same amplitude. Constructive and destructive interference result from the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, surface water waves, gravity waves, or matter waves. (...) Consider, for example, what happens when two identical stones are dropped into a still pool of water at different locations. Each stone generates a circular wave propagating outwards from the point where the stone was dropped. When the two waves overlap, the net displacement at a particular point is the sum of the displacements of the individual waves. At some points, these will be in phase, and will produce a maximum displacement. In other places, the waves will be in anti-phase, and there will be no net displacement at these points.

By the way, this is the reason why microwave ovens have rotating plates. Inside those ovens the microwaves are stationary, with regions of constructive and destructive interference. You have to move the food around so all parts of it are exposed to constructive interference, otherwise some bits are not heated by the radiation of the oven.

Back to magic. Mana is everywhere, mostly as stationary waves that go north and south. Where they meet constructively you call it a ley line, where they meet destructively you call a dead zone. Now due to the physics of magic, thaums travel perpendicular to the wave, so what you are measuring going east to west is the thaumaturgical flux.


Destructive Interference

Lots of excellent answers here! There's another one that talks about wavelengths, I'd like to focus on the effects of interference.

Imagine all the different ley lines had a particular frequency that they operated on. As mentioned elsewhere, different people could be tuned into different frequencies, allowing them to use different types of magic. But the thing about wave frequencies is that when they combine, they can either boost or inhibit each other (https://en.wikipedia.org/wiki/Wave_interference). If certain magics were in or out of phase with each other, you could have it so that some ley lines crossing boosted both magics, some crossing deadened each other, and the combination of all ley line types crossing resulting in total destructive interference, where all the frequencies perfectly cancel each other out.



In the real world, magnets interact in many entertaining and surprising ways, including cancellation: the creation of magnetic "dead zones" when multiple magnets are in close proximity. This works because the magnetic field at any point in space is the sum of the magnetic field from all individual sources -- so if one field points in one direction and the other points in the opposite direction at some point, the net field is zero.

However, as you can see in this example, the "dead zone" created by two simple magnets isn't exactly where you want it to be -- it's inside the angle they form. In addition, simple magnets have the unfortunate property that they have physical mass and cannot be perfectly superimposed. Thankfully, our increasing scientific understanding of electromagnetism has exposed us to magnets which suffer none of these limitations.* I refer, of course, to electromagnets.

The flow of electric current also generates a magnetic field. That means that by directing current in particular patterns, you can generate particular configurations of magnetic fields. One of the most common patterns calls for looping wire around a nonconductive core to form a "solenoid": a conductor which produces a magnetic field pointing straight in one direction (inside) or the exact opposite direction (outside).

So, "magic" is electricity, but conducted only by certain structures that have no physical mass (and preferably a minimum of direct interaction with mass, period). Where these structures loop tightly, resembling solenoids, magical force is generated -- and anything capable of interacting with (or being interacted with by) magic can convert that into power. The force is strongest inside the structure (along the ley line), has less energy outside, and drops off very quickly as you get further away. That force can be used to power the movement of stuff (teleporting people, crystal ball images, whatever) from one place to another, particularly if sent along a ley line. The simplest magical activity will involve simply sending things along with the current, pun fully intended. As practitioners becomes more sophisticated, they will develop ways to translate that raw motive power into other forms of energy, most notably mechanical energy -- the magical equivalent of a (living) electric motor which can power almost anything. Where two of these ley lines intersect, provided they are running in almost-opposite directions, the magical fields nearly cancel and we are left with a magical dead spot.

Now, before you stop with this simpler approach, think it through carefully: it has some implications. In particular, the political geography of your world will be weird. It's very likely that people in your world won't know why things don't transmit past ley line intersections, because much of the area around the dead zone will be hazardous or lethal for anything magnetic -- er, susceptible to magical force. So your magicians may not know that their spells fizzle in the intersection, because they'll be too busy avoiding the fact that their spells explode in the penumbra! If magical ability is an intrinsic gift that can't be turned off, it's even worse: normal people are able to travel freely while magically talented people may be hemmed in by the closest ley lines to their place of birth, unable to touch these invisible boundaries without suffering the same fate as a human who touches a live wire.

Moreover, ley lines based on this model are directional: perhaps a sending in one direction can work on the basis of the magician's power alone, but a sending in the other direction might require a wand and a rare gemstone placed in a certain configuration, the magical equivalent of a simple machine. Perhaps some forms of magic, such as lightning or telekinesis, naturally "flow" in the parallel direction if not deployed by a sufficiently skilled mage. Don't cast that fireball upwind!

If you're not a fan of these complications, or you want a more arbitrary ley line configuration, you'll need to add a few extra dimensions to your world so that the magical fields can run antiparallel in some dimension we can't perceive.** Magical fields no longer point along the ley lines; the ley lines are simply magical fields centered on some other 3+dimensional space that intersects with the 3-dimensional space we can perceive. (Strictly speaking, they're probably ley planes, but that doesn't have the same alliterative appeal.) The actual force vectors now point out of our space of existence.

To use magic, then, a magic-user reaches out (some possibly-immaterial part) perpendicular to their universe in higher-dimensional space so that the magical fields can act upon them, generating force which they can then channel to their own purposes. However, where these fields intersect (but point in opposite directions), there's simply no net magical field and thus no force can be generated no matter how the mage moves (unless they move within the visible universe -- i.e., leave the intersection).

Bonus: if ley lines are equivalent to higher-dimensional magnetic fields, you can introduce objects and people that look normal but have the properties of solid, static magnets and behave in wacky ways that are almost totally incomprehensible to the mere mortals who observe them.***

*Well, okay, maybe not none: a real electromagnet requires something to carry the electricity, and that conductor itself must have mass.

**To understand how this works, picture three planes superimposed. Leave one perfectly flat, slightly tilt one north/south, and slightly tilt the third east/west. The first is your world and the latter two are your ley lines. They run perpendicular from the perspective of your world, but in the higher-dimensional space they are very close to parallel -- and if they "point" in opposite directions, the fields will almost cancel where they intersect. Now repeat the visualization in three dimensions, and Bob's your uncle.

***NSFW for profanity. But come on, if you read through this whole post without expecting this joke…


You can base your principle on basic biology like Osmosis.

In normal area the environnement is Hypertonic:
Organism radiate their inner mana.
That's why you can see someone mana around him like a thin steam. By voluntary stopping this flow of mana from the body, One can make their presence much harder or even impossible to sense.

In Dead zone, the environnement is Hypotonic:
When the mana concentration exceed the body mana concentration.(Note we are using concentration instead of volume) Environnmental man flow into the body. As the body is not able evacuate the mane it inervetabily burst.

Using concentration allow you to have people training to be able to go at the edge of the dead zone. And having a surprise mythical beast in the center, a beast with a high mana concentration.

For the lethal explanation :
You can have many level of mana poisoningbased on the amount of mana overflowing from the body.
The manbrane/bridge/chakra/mana vein could simply break/explode when receiving too much.
You can have the mana inversion.


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