Pyromancy: How Does Fireball Work?

Magic fire – is it impressive or merely impractical?

Moths to flame

Pyromancy, pyrokinesis for the contemporary and sci-fi settings, and general fire-based magic, is a well-worn trope in fiction. Throwing fire around is a fun high-spectacle feature to include in a story. It’s easy access, everybody knows what fire is and as a species we’re pretty enamoured with it. But pyromancy in fiction is usually only shown in a very specific context – if there’s danger, burn the general vicinity of said danger and if that doesn’t solve the problem you weren’t using enough fire. The subtext of fire in stories often serves as a symbolic representation of a lack of control. Usually, the hothead character with anger management issues will stub their toe and accidentally incinerate the local orphanage. Their arcs ends up being an Aesop on self-control or the benefits of some form of therapy. Too often, despite the narrative aesthetic of volatility, fire is, ironically, very much only out of control if, and only for as long as, it’s necessary, in order to demonstrate the consequences of emotional people with destructive capabilities. In behaving as such, pyromancy can often undermine its own subtext and symbolism and behave more as a sort of heat-addled power fantasy than a coherent bit of the setting.

Flint meet tinder meet house

I didn’t really want to focus in on fireballs because they’re such a tropey narrow-focus single-issue thing, and there’s a significant number of more broadly applicable uses for pyromancy that are, honestly, somewhat more interesting. However, as a great deal of fantasy and science fiction uses pyromancy in an exclusively violent context, the go-to illustration of pyromancy is the fireball. The fireball is worth dealing with, therefore, because it gives us some easy-access groundwork for figuring out the ‘mechanics’ behind the idea before we move on to the broader considerations for a narrative and setting.

Two things before we continue:

It should be noted that my relationship with physics is at best a passtime curiosity. So, while I’ve attempted to be reasonably thorough in my research, the extrapolated conclusions may not be air-tight. On the off chance that a physicist, engineer, or someone better educated is passing by, I invite you to make Swiss cheese of my assertions.

To the other matter – yes, this concerns magic, and so doesn’t have to translate 1:1 with the real-world laws of physics. However, unless specifically demonstrated to the contrary, your audience will have take their base reality – the basic laws of physics for example – as the default. I’ve noticed that anyone who, like myself, is a tedious enough human to feel a profound necessity to deconstruct bits of fiction like this, also seems to feel the need to make an awkward and laboured pre-apology to the inevitable loud response championing people’s right to do whatever they want with magic and blah blah blah: Yes. This is not an attempt to ‘well actually’ my way through fiction. This is a fun exercise in deconstruction. Everybody knows we’re discussing magic and magic doesn’t require thesis-level accuracy. The fact of the matter is that this is several thousand words on the concept of pyromancy in fiction, with the possibility of several thousand more to follow. I can only conclude that I am an incredibly sad man… So before you all-caps your objections into the comments so you can make excuses for your deus ex machina plot holes: Shut up.

Real-world pyromancy

Like most magic, pyromancy in the real world originates in a form of divination. Ancient people were really keen on trying to figure out what the future held for them so they could side step dying of the plague or dysentary or an infected parchment cut, and so they were down to listen to any and every smooth-tongued charlatan that rocked up, glanced at their hearth or some leaves or inhaled a bunch of hullocinogenic fumes or ate some curious fungi, and yammered off the numbers to the local medieval lottery, etc. Whatever the case, off went Good King Wenslas to become Good King Wins-less. Then he would spend all night wondering whether he got conned because someone saw him for the giant mark that he was, or whether he didn’t win the medieval lottery because God was angry with him for having sexual thoughts about the neighbour’s yak the other day…

In fiction, pyromancy is somewhat more practical. While various creators across various mediums have depicted fire based magic in a number of ways – with A Song of Ice and Fire demonstrating both traditional divination-based forms of pyromancy and decidedly not-so-traditional forms, while games are quite happy to let every random git in a robe and a pointy hat slam burning meteors into the planet, in order to slightly inconvenience whatever happens to be directly in the line of impact… Regardless, and because magical meteors are a whole other kettle of fish, the basic and arguably best-known example of pyromancy, is your bog-standard sod lobbing gobs of fire about the place. Because who cares about consequences? So how exactly does one go about said lobbing of fireballs?

Fireballs, how do they work?

Pyromancy comes in a couple of different flavours: The first requires some sort of reagent. Need fire? Carry a lump of coal, soak a glove in oil, dress up like a candle. It’s effectively a variation of sympathetic magic, drawing links between an intention and a result is a part of real-world magic tradition/occultism and is very old. Think any time you’ve ever heard ‘Jill wants to shag Bob, so Jill yanks out Bob’s fingernails with a pair of hot pliers so she can make a magical lust charm out of them’, that’s basically what this is. It’s a pretty good way to translate these abstractions nicely to the audience by linking the concept of creating fire with sources of combustion that they know and understand. It’s not scientifically accurate, but it doesn’t have to be – that’s where the concept of magic steps in to bridge the gap and create the suspension of disbelief without feeling cheap.

The second is ‘I’m holding a ball of flame now because fuck you’. It’s based in rule-of-cool and, honestly, nobody wants to walk around fondling a pocketful of guano in order to set Morgoth larpers on fire. On the other hand the ability to make fire without the necessities apparent does raise questions for some of the more anal-retentive in the audience.

Fire requires three things: heat, fuel, and oxygen. The general rule seems to be that if something isn’t on fire, you’re not using enough heat . Rafael Viñoly is a lad. So, if you want fire, make heat. However, humans make good kindling what with all the meat and fat, and so one of the considerations when trying to conjure your fireball is simply how much heat your pyromancer can create without immolating themselves in the process.

This immediately raises questions as to how a pyromancer goes about making fire anywhere in their vicinity without igniting their own bodies or suffering various heat-related trauma. Theoretically your pyromancers need to be somewhat more heat-resistant than the average idiot merely to fulfil their role without turning their own bodies into tasty candles. But because that seems like its own subtopic of a larger concern, we’re going to table that one for the moment and maybe circle back to it at a later date.

If you’d like your pyromancers to stand around cradling a hand full of fire like a wine glass, sans a source of fuel, well, you can’t strictly do such a thing – there’s no real getting around the fact that you’re going to need fuel – but you can create the illusion of not needing it. You might immediately object, something along the lines that if the fire is composed of ‘magical’ flames then you can sidestep the fuel part and get straight to the burning. I have no real objection. However, as various people pointed out while I was researching – in every case of ‘magical’ fire, said fire acts exactly like normal fire. So with that in mind, we’re going to assuming the happy magic fire people are just conjuring regular fuel–heat–oxygen fire.

Fine, Dr. No Fun,” say you. “Just tell me how to get my fireball.

Your first option is hydrogen.

K. My character pulls hydrogen out of the air. Done. Fun now…

Hydrogen in the air makes up about 0.00005% of the atmosphere. So, if your pyromancer is trying to rip hydrogen out of the air, they’re going to begin pulling hydrogen to themselves, about 84 years later they will have accumulated enough hydrogen to make and sustain a flame the size of an average apple. So maybe not. But you can rip hydrogen out of water vapour, which amounts to, depending on the temperature, between 0.01% and 4% of the atmosphere. This may not sound like a great deal, but apparently this is more than adequate – enough so that we are trying to develop ways to cost-effectively pull hydrogen from the water vapour in the atmosphere in real life. As you might expect, currently electrolysis uses more energy to harvest the hydrogen than can be made, and so we can conclude that it’s a pretty intensive process. On the other hand, it does point to water vapour as a practically omnipresent source of fuel for your fire magic and so pyromancers can just stand around making fire out of apparently sod all.

Ok, granted at this point I’m just splitting hairs with this whole distinction, but bear with me.

There’s no actual way to convey the idea that a character is using hydrogen as fuel for their pyromancy by splitting water and hydrogen molecules apart. But consider how energy intensive that is. What kind of exertion and concentration do you have to do in order to start pulling bits of the atmosphere into their component pieces purely so you can get the fuel to chuck a bit of fire at some chump? So far, this is an intensely expensive process. In turn, that means that there’s a reasonable chance that doing pyromancy this way is a pretty heavy exertion. I would expect that actually being able to do any pyromancy, let alone the sort of high-octane pyrotechnics that we usually associate with the idea, is the reserve of the kind of people with a lot of will power, and a great deal of training and/or focus. Far from being baby’s first spell, the cost of doing business is prohibitive to the point that it may just not be worthwhile.

It gets more interesting. Your pyromancer chucks their fireball. Unless you’re aiming at a bale of hay or something highly flammable, just throwing a bit of fire isn’t going to be all that effective. The spell might singe some hair and cause superficial burns, but generally when fireballs are presented they’re not powerful because they’re incredibly hot, they’re powerful because they go boom. You need an explosion.

I cast grenade

So now you need to make something explode. An explosion is effectively an expansion of gas created by a relatively fast series of consecutive reactions. Accelerationist ignition. A wood log will burn because the reaction releasing the energy is relatively spaced out so the stored energy is released over a longer period of time. By comparison, gunpowder is explosive because the chain reaction occurs rapidly, releasing the same energy over a far shorter length of time. But if you just set a pile of gunpowder alight on a table the resulting explosion isn’t much to write home about. Even if your fireball’s energy consuming reaction is fast enough to make it explode, that explosion will only ever be of relatively limited efficacy. If you want to amplify an explosion, you need to contain the gasses, creating an accumulation of pressure as the gas expands but has nowhere to go until the pressure forces a breach of containment.

The strength of the explosion depends on the magnitude of confinement which in turn depends on the degree of confinement and could generate a blast wave that can produce damages to the surrounding buildings and people (Baraldi et al., 2009).” 

If you just want to light a torch or something, there’s nothing to worry about. Heat whatever you’re using for fuel until it ignites. If you’re throwing fireballs around, things get more interesting because, presumably, you’re attempting to do as much damage as you can. You can throw a bunch of flames at someone and it might burn them, it might set them alight, there might be a minor explosion and a bunch of smoke, but it does seem to be potent enough to immediately immolate anything. While this does seem insensitive to burn victims and anybody who has ever had to undergo reconstructive or aesthetic surgery due to an improperly handled firework, for instance (the social ramifications of which are easily a hundred times more interesting from a story perspective than saving the world or whatever), it does seem to suggest that the usual portrayal of the archetypical fireball is substantially exaggerated.

So theoretically what you want is some sort of explosion on impact. In turn, that mean you need to be able to contain a lot of gas in some sort of magical fire bubble. When your magical fire bubble bursts, the intensity of the explosive energy release is going to imply a number of interesting considerations.

Proximity to the blastwave is going to make a dramatic impact. The closer you are to a blast, the more of the wave/force you get hit with, effectively. The further away you are the less concerned you need to be. Sounds fairly obvious in retrospect, but it’s a detail that is worth considering.

Surroundings are also going to affect the behaviour of the blastwave and, in turn, the impact on characters and surroundings. If you’re outside, not too close and the force is not too great, you should be ok. If you’re inside you want to be far away. This is because the energy in the blastwave doesn’t just instantly dissipate. It rebounds off any surface it comes into contact with – walls, floors, ceilings, your mum, etc.

Following this, consider damage. For instance, shockwaves can apparently have a great number of interesting effects on our supple meaty carcasses. They can rupture membranes, like the ones in your ears, they can damage your organs, like your lungs and heart. Fun fact – humans are largely sacs of air and liquid containing smaller sacs of air and liquid. Just think about any part of your body that functions as a sac of some kind and understand that if you disrupt the complicated meat physics of flesh, air, and liquid, then things get very traumatic very quickly. It turns out that a shockwave is a fantastic delivery vehicle for that type of disruptive trauma.

Finally, let’s consider displacement. What’s lying around, like debris. Which is to say that you ought to hope that the majority of it is neither heavy nor sharp. If your scene contains a lot of shattered glass, splintered wood or bits of jagged rock, then explosions are going to throw all of those all over the place. A particularly violent explosion is going to transform your fireball into a nailbomb.

If your character is caught in the blast of your fireball, do they stagger? Do they fall down? Is it possible that they could be knocked off of their feet or even hurled through the air? You’d probably need something pretty intense to get the latter effect, but as I noted at the start, my understanding of physics is ropey so I just tend to rely on some educated guessing and some cautious estimation. Finally, as much as I try to treat the rule of drama and the rule of cool with a great deal of caution, it should go without saying that for the purpose of fiction, use your own discretion. Does it work for the story if you hurl that bitch into a wall? Then hurl that bitch into a wall!

Then you’ve got structural concerns. If your characters are indoors, are there any old or weak structures around, if you’re outside, consider whether there are any rotting trees or things of that nature. A strong enough blast is going to knock all of those over. Collapse a ceiling, knock some stones loose, that kind of thing. Given that pyromancy and pyromancy-adjacent magic tends to turn up in fantasy settings, if the scene is happening in an urban environment a fair number of buildings might be wattle and daub huts, small stalls, or anything similar. Even if you don’t set anything alight, if you throw a fireball in a small hamlet, you might accidentally obliterate people’s houses and/or businesses. Even if the main structures are solid enough to withstand a moderate blast, there’s a good chance the roofs are thatched. Like I said, not a physicist, but I don’t think it’s a stretch to suggest that you’re going to need to call a thatcher. 

Taking all of these factors together, the go-to illustration of fire magic as a ‘fire and forget’ projectile, becomes something very wild, unpredictable and potentially very difficult to control spell that might deserve a little more caution.

The nuclear option

Speaking of things that are difficult to control, somewhere a few paragraphs ago, I indicated an entirely different method of generating fuel for a pyromantic flame. You’ve figured it out already – and yes it’s about as absurd as it sounds: fusion/nuclear reactions.


This doesn’t require a great deal of elaboration, suffice to say that it is an exceedingly bad idea. On the other hand, it is also pretty funny. It’s a bad idea to use nuclear physics to make a rock-sized glob of flame, but for the sake of thoroughness and humour, here’s how this idea works out:

First, the sheer amount of energy you need to expend in order to split a sodding atom in order to do absolutely anything in the relatively limited number of practical pyromancy applications like lighting a torch, staying warm, or cooking food, is so wildly beyond necessity as to negate the need for pyromancy in the first place. If you can casually split the atom then lighting torches and throwing fire balls around is the least of your concerns. If your character is causing nuclear fucking explosions in order to light a campfire, the campfire no longer exists. Nor does your character any more. Nor does anything for miles around it. The entire area is a nuclear wasteland. Because your pyromancer wanted to heat up some beans or something.

Furthermore, the heat generated is in the hundreds of thousands to millions of degrees. The flash of light created by igniting the campfire will blind everyone in a 10 mile radius. 150 decibels will burst your eardrums, 200 decibels can kill you, and a nuclear explosion goes off at well in excess of 200 decibels. The noise alone may actually be lethal. Finally, if you somehow manage to work around all of that, there’s the nuclear radiation to consider. Even if your pyromancer character somehow survives causing a nuclear explosion, the sheer horrifying dose of radiation will kill them and anybody with enough plot armour to survive, in a matter of days. So let’s not.

Pratchett had a point.

If you’ve ever played Divinity Original Sin II, you’ll appreciate how out of control fire can become, you’ll appreciate the capacity for fire to turn a well-managed situation into a sudden uncontrollable scramble in a matter of seconds. If you expand on that idea beyond the well-managed confines of a video game, accounting for all the extra variables and concerns of reality, you can extrapolate how complicated something seemingly quite simple can get.

Fireballs are probably relatively ineffective cantrips if they don’t detonate. Alternatively, if they do detonate, then they are very unpredictable, volatile, and potentially very scary. If your fireballs are explosive, then you almost can’t miss with them. You can only be incrementally less effective. You also have very little control over who is affected by them. Fireballs are usually presented as one of those things that a character lobs at someone, and then moves onto someone else – it’s almost functions like a gun: shoot and move onto a new target. However, when you consider the ‘reality’, for lack of a better word, you may actually be throwing some kind of supernatural bomb.

This means that every time you see a sorcerer of some kind casting fireball in a book, videogame, film, and so on, there’s a significant chance that the sorcerer will harm themselves, anybody they’re with and anybody in the vicinity. Which means you can’t even throw these things around on a battlefield all that much, unless you’re relatively certain of only hitting enemies or you’re not particularly concerned who gets hit. Arguably, pyromancers in war become some sort of magic artillery. After that there’s all manner of secondary and tertiary considerations – the obvious one is starting a fire. Any flammable material in an urban environment and you stand the chance of burning a whole settlement to the ground. We’re just going to take it for granted that nobody is throwing fireballs about in a natural environment with dense vegetation, like a forest. If you’re in an enclosed space then the potential for terrifying internal injury increases.

Pay attention to Terry Pratchett. Underneath all the humour, the witches in his fiction always embodied a pragmatism that, on the surface, seems at odds with their careers but is revealed to be nothing more than normal practicality on further consideration. Take Agnes Nutter of Good Omens:

And precisely because she was a witch, and therefore sensible, she put little faith in protective amulets and spells; she saved it all for a foot-long bread knife which she kept in her belt.

Pyromancy seems to be one of those things that is deceptively unintuitive. What do you want to do? Hurt a bloke from a distance. Ok. Throw a rock and move on. The archetypal ‘fireball’ effectively just replaces the rock. When you get down to it, fireballs might actually be the least effective way to use pyromancy in an offensive context. The amount of energy it’s going to take to rip hydrogen atoms out of water vapour seems prohibitively expensive and if all you really need to do is heat things up, why not just heat up your enemies? You don’t need a ball of fire – it’s one of the least effective methods of winning a violent conflict. It might just be more cost-effective to stab a bloke.

So why is this more interesting than some mug in a bathrobe lobbing a ball of fire at a dragon and having it be roughly as useful or useless as the scene dictates? In stories, fire is usually shorthand symbolism for power. We evolved to use tools because an ape was smart enough to make sparks and then breed. A pyromancer’s ability to control fire is a primordial dick on the table moment. If you can’t match that pyromancer’s ability to make fire, you have the smaller dick. But the thing about power is that it’s complicated. As the old saying goes ‘I want, doesn’t get’.

Complexity and chaos

Stories run on things going wrong. The better you understand anything, the more complex that thing becomes. The more complex that thing becomes, the more points of failure there are. The more points of failure there are, the more variables, and thus stories or permutations of stories, there are. The first question is, naturally: What does your pyromancer do when fire won’t help? The follow ups might be, what does your pyromancer do when fire would help they have nothing to burn? What do they do when fire would help but they have no oxygen (aside from suffocate)? What do they do when fire goes wrong? And on and on and on. Some of these might not yield you an award-winning novel, but they’re worth considering, if only as thematic highlights. ‘A pyromancer’ is cool for about ten seconds before they’re just a generic smear with central heating. ‘This person who happens to have pyromancy as a skill, but is not completely defined by it’, while a bit of a mouthful, is more interesting and makes for, potentially, a better story. 

This works for any magic or technology. If your magic or technology is a win button, you’re not doing it right. Your story comes from complications. Pyromancy, therefore, is a tool. No tool fixes everything, and the more complicated the tool, the more interesting the results of it breaking can be. People have a fairly intuitive understanding of fire: ‘don’t touch it, but it can be useful’. Pyromancy, as an extension of this, usually begins and ends at ‘it’s useful’. It might be worth considering what’s going on under all the heat and flame, because fire is anything but simple.


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