The most important question for a GM (or other players) to ask when the party spellcaster enthusiastically yells, “I cast Fireball,” is “are you sure about that?”
\n![\"A](\"https://media4.giphy.com/media/v1.Y2lkPTc5MGI3NjExaWU2YXJtbWxkbWk1dTlrYm81bmg2bnl2d2VzdTlyeTB5Zm12cXdmaCZlcD12MV9pbnRlcm5hbF9naWZfYnlfaWQmY3Q9Zw/WIwPIds4m1CJG/giphy.gif\")
\nThe most important question for a GM (or other players) to ask when the party spellcaster enthusiastically yells, “I cast Fireball,” is “are you sure about that?”
\n\nLet’s start with some context: IRL, one of the things I do is volunteer as a firefighter, so I have a little bit of experience at observing fire behaviour outdoors, and have seen more than enough training video about fire behaviour in enclosed spaces to be very wary of it. I've also both GMed and played when Fireball has been cast and the physics and chemistry of what should happen not been considered; the magic fire just burns. Even better, I have been at the hot end of a Fireball going off when a clever DM did understand the consequences and let the party experience them first hand.
\nAs one of the defining spells of the D&D experience, Fireball is going to be cast by one of your game’s magic wielders at some point. But have you, or they, considered how fire and explosions behave, and what that explosion might do if it’s not in the middle of an open field?
\nLet's quickly take a look at what the current 5e and 5.5e descriptions of Fireball have to say.
\nThe 2014 Player's Handbook block for Fireball reads:
\n\n\nFIREBALL
\n
3rd~level evocation
Casting Time: 1 action
Range: 150 feet
Components: V,S, M(a tiny ball of bat guano and sulfur)
Duration: Instantaneous
A bright streak flashes from your pointing finger to a point you choose within range and then blossoms with a low roar into an explosion of flame. Each creature in a 20-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 8d6 fire damage on a failed save, or half as much damage on a successful one.
The fire spreads around corners. It ignites flammable objects in the area that aren't being worn or carried.
At Higher Levels. When you east this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.
So far, so uncontroversial. How about the 2024 version (which is the same in the SRD 5.2.1, as expected):
\n\n\nFireball
\n
Level 3 Evocation (Sorcerer, Wizard)
Casting Time: Action
Range: 150 feet
Components: V, S, M (a ball of bat guano and sulfur)
Duration: Instantaneous
A bright streak flashes from you to a point you choose within range and then blossoms with a low roar into a fiery explosion. Each creature in a 20-foot-radius Sphere centered on that point makes a Dexterity saving throw, taking 8d6 Fire damage on a failed save or half as much damage on a successful one.
Flammable objects in the area that aren’t being worn or carried start burning.
Using a Higher-Level Spell Slot. The damage increases by 1d6 for each spell slot level above 3.
So, similar enough to the 2014 version so as to make minimal difference for this post's purposes, except that it doesn't mention the spread effect, which will be an important part of the discussion below.
\nFor the purposes of the sourcebooks, and playing the game rules-as-written, Fireball would appear to manifest, burst into flame, and vanish, more or less instantly. However, if you want to play a more interesting and realistic homebrew, I've done some description and analysis below that you might want to use whole cloth or in part.
\nA little sulfur and a little bat guano. What's happening here? In terms of the incendiary and explosive chemistry it's important.
\nSulfur is flammable, and this property has been known and understood in written texts since pre-Christian times. It was certainly being used by the Chinese as a component for black powder by 808 AD. Chemically, gunpowder deflagrates (burns slowly) rather than detonating. Sulfur here is acting as a fuel and accelerant.
\nBat guano has been used in Mesoamercian civilisations as a crop fertiliser for over 1000 years, and in the West since the early 1800s. It is a rich source of nitrogen, potassium, and phosphates. Guano can be processed in kilns to produce potassium nitrate (saltpetre, KNO3), another major component of gunpowder.
\nIn combination, sulfur and potassium nitrate are two of the principal components for gunpowder (along with carbon). The sulfur reduces the temperature necessary for ignition and serves as a fuel and the potassium nitrate breaks down during the ignition reaction to provide oxygen.
\nFor D&D purposes, let's assume that our two components form a magical, carbonless gunpowder under high pressure and containment (that's how you get gunpowder to detonate rather than deflagrate) that ignites rapidly (thanks, sulfur) and changes state from compressed solid to aerosilised powder or gas and burns hot and fast (thanks potassium nitrate).
\nAt this point we have a basic chemical how for a Fireball. It's the what happens where this starts to get interesting. To horribly misquote Douglas Adams in The Hitchhiker's Guide to the Galaxy:
\n\n\n“Fireball is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to a fireball.”
\n
The sourcebooks have always described Fireball as a \"20' radius sphere\". That's fucking enormous. By comparison, a 10m diving platform tops out a hair under 33'. Imagine a ball of fire with x, y, and z axes all larger than the height of a diving platform.
\n![\"Comparison](\"https://stephencollins.org/media/posts/9/fireball.webp\")
\nBut how big are we really talking? The volume of a sphere with radius 20' (~6.1m) can be calculated with the formula:
\nV=4/3πr3
Wolfram Alpha tells us that's 33,510ft3, which is 948.9m3 in not-USA numbers. Here's where the bat guano hits the fan.
\nThe spell description states, \"[a] bright streak flashes from you to a point you choose within range and then blossoms with a low roar into a fiery explosion.\" Based on the physics and chemistry that we're very much glossing over here, but paying a little more attention to the firefighting training I've received, a few things are happening. Let's enumerate them:
\nNow, if we're in an open field, an arena, a large temple, a big cave or other large open space we're doing okay here and our spell goes off doing the expected 8d6 damage to whatever foe happens to be standing in the way.
\nBut we're not here for the easy way out, are we?
\nAs we've postulated above, the cloud of gas or dust that is the fuel for the fireball expands and fills the available space evenly out from the point of origin. Again, if we're in a big open space and we cast that point of origin to be 20' or more above the ground, we get a standard Fireball. In explosive terms, that's an air burst.
\nBut how often in our games are we in places like that when we feel the need to cast terrifying death flames? Not often I'll warrant. Far more frequently, we're somewhere at least partially enclosed.
\nSo, what's going to happen? I'm glad you asked.
\nFrom our math above, we learned we generate 33 thousand-ish cubic feet of fire once the Fireball goes off. Exciting! If we think about that in terms of D&D's stereotypical map of 10' cubes, that's 33-and-a-bit of those cubes we're about to fill with fire. Thanks to the generosity of Dyson Logos, we have a wealth of maps we can demonstrate this on, but let's choose this one - The Ancient Temple of Torrel. Let's make some helpful assumptions about this map and place ourselves and some foes on the map:
\nOur party is made up of :
\nThey have just emerged from the stairs connecting Level 1 to Level 2 and entered the large hall on the second level. At the far end of the hall, their presence has disturbed a pair of now-irritated minotaurs, who look to be about to engage. Initiative is calculated, and for whatever reason the Fates have chosen, our friend Flamdoosip goes first, announcing, \"I cast Fireball!\"
\n![\"A](\"https://stephencollins.org/media/posts/9/ancient-temple-of-torrel-level-2-850x350-72dpi-web-initial-encounter-close-up.jpg\")
\nAt this point, our DM, aware of the discussion we've been having here, and a touch amused by the chance of a TPK through misadventure (and inclined to allow a do-over if things go very badly), lets the spell be cast, asking where the wizard is casting the origin point.
\nWhile blessed with good Intelligence, our wizard has low Wisdom, his player having chosen that as a dump stat. He targets the spell to the wall between the columns behind the minotaurs, and 10' off the floor, as it's the furthest point available in the hall. Not the worst decision in the circumstances; he's allowed for the radius of the sphere to be far enough away not to blow back on the party, but has completely failed to account for the fact they are in an enclosed space.
\n![\"The](\"https://stephencollins.org/media/posts/9/ancient-temple-of-torrel-level-2-850x350-72dpi-web-fireball-cast-close-up.png\")
\nLoosing a Fireball in this space results in what is effectively a ground burst. The fireball has nowhere to go except expand out from the wall and into any nook or cranny it can find. Shit is, as they say, about to go down.
\nLet's see how much space this fireball takes up. As we know, it has a volume of 33,510ft3, or 33½ 10'x10'x10' cubes. Real-world physics indicates that the aerosol/vapour will fill out to any place it can. If it ignites in the process, the flaming ball will behave similarly. The pressure wave and flame from the blast will smash open doors, climb the stairs to level 1 and descend the stairs to Level 3.
\nWhat does that look like (I don't have the skill to animate this, so you're going to have to be satisfied with the after version)?
\nThe image below shows the spread on Level 2. I've decided the pressure wave can't blow counter-swung doors out, though in reality, it probably would. I've also not mapped the effect on Levels 1 and 3, so the spread shown is about 75% of the full potential spread.
\n![\"A](\"https://stephencollins.org/media/posts/9/ancient-temple-of-torrel-level-2-fireball-effect.png\")
\nThe 2024 Player's Handbook states that Fireball deals equal damage to all creatures in the blast, so rolling we get 29hp damage. There's a chance to reduce damage to half with a successful Dexterity saving throw.
\n\nLet's see how those saves go against the DC 15 Flamdoosip casts at. For simplicity, I'm going to assume each monster and character has the stats either in their 2024 Monster Manual stat block or the standard class array on p38 of the 2024 Player's Handbook:
\nAt this point, even if we got excited about flame spread, we could stop our exploration. But who wants that!? There are several additional effects we can explore that would happen in the real world. Whether you might choose to include them in your homebrew is up to you, so I'll include some possible in-game consequences.
\nWe already know our standard Fireball spell produces Fire damage. The 2024 Player's Handbook describes Fire damage as \"Flames, unbearable heat\". But how hot and how much catches fire or is burned or vaporised?
\nThe real world thing a Fireball most closely resembles is a backdraft (rapid introduction of oxygen to a fire) or flashover (heat ignition of smoke particulates). These phenomena are both rapid accelerations of fire with spectacular effects. In volunteer firefighting, while we train to prevent, identify, and manage both, the flashover is the most likely. ISO 13943 defines flashover as a \"transition to a state of total surface involvement in a fire of combustible materials within an enclosure.\"
\nIn heat terms, a flashover burns around 1100℉ (nearly 600℃). At that temperature, plate metal armour may warp and chain and other piece armour is likely to burn into the skin and muscle beneath, and it is well above the temperature necessary for 3rd degree (full thickness) burns. It's not quite as hot as is needed for a cremation. Clothing and leather will be carbonised.
\nTranslating these kinds of temperature and fire effects into D&D is pretty difficult if you want to maintain a survivable fantasy world, so I'm not going to try.
\nWhat you might choose to do is have the players experience irrecoverable damage to their equipment that requires rapid back out from the situation, a return to camp for fresh clothes, and travel to the nearest town or village for repairs and replacements for damaged armour and clothing.
\nThe other type of injury a PC might experience thanks to a Fireball is blast injury. That's exactly what you think it is. The US Department of Defense Blast Injury Research Coordinating Office describes it as:
\n\n\nA blast injury is a complex type of physical trauma resulting from direct or indirect exposure to an explosion. Blast injuries range from internal organ injuries, including lung and traumatic brain injury (TBI), to extremity injuries, burns, hearing, and vision injuries.
\n
That site also goes into detailed analysis and description of blast injuries that may be of interest.
\nIf one was inclined to play hyper-realistic injury effects in TTRPGs, you could build mechanics for this. I'm sure there's at least one system out there where it's been done (leave a comment if you know one so I can take a look).
\nIn game terms, you could take an easier approach and apply an additional set of Bludgeoning damage at 4d6 to creatures and PCs caught in a Fireball. TPK isn't usually a desirable outcome, so judicious application of this probably makes sense.
\nEnvironmental damage is a consequential and serious outcome after a Fireball. Wooden furniture will be reduced to char, doors opening away from the ignition will be blasted open and off their hinges and counter-swung doors will be severely charred, if not also blown out, depending on how far from the ignition point they are.
\nImplementing completely realistic physics, chemistry and consequences of a Fireball at your table is probably neither easy or entirely desirable. However, I hope I've given you enough fuel (pun intended) here to add a wealth of colourful description to the next time an over-eager spellcaster lets off a Fireball indoors. Plenty of what's here can be used without destroying the party or unbalancing your game.
\nPlease let me know if you enjoyed this post, and particularly if you'd like me to explore more real-world spell effects.
\nI was given the Red Box Basic Set as a Christmas gift from my parents in 1981 when I was in the 7th Grade. I’d played my first game of D&D earlier that year. Christmas that year was with my paternal grandparents; a more arch-conservative, closed-minded pair of people you’d be hard put to meet.
\nI was incredibly excited to receive this gift. It was much-wanted and I spent the days following Christmas poring over the rules and The Keep on the Borderlands; at least when I was permitted to be inside to read, as my grandparents were firmly of the belief that children should be seen and not heard, and certainly not inside reading during daylight.
\nI do not have fond memories when I remember the long drive home. My Mum was very upset. My grandparents had made it clear to her that they believed her to be an unfit parent for buying me the Basic Set. I was sure to end up corrupted and an outcast—both true in a sense, but never in a bad way 😉
\nThe following year, my high school was one of the first in Canberra to get personal computers, with a couple of VIC-20s and an Apple II. Immediately hooked, I bought a VIC-20 computer of my own that I saved for with pocket money. Two years after that, I upgraded to a C-64, which lasted me through university. Attack of the Mutant Camels and The Hitchhiker's Guide to the Galaxy, among others, became my go-to entertainment.
\nInterestingly, Christmas the following year ended up much the same when my sister and I were both given variants of the original Donkey Kong Game and Watch, surely another gift that would rot our brains and make us unsuitable members of society.
\nUpset mother notwithstanding, Christmas 1981 kicked off a lifelong (so far) love of TTRPGs and boardgames, though the boardgame enjoyment came a little later. There's a cupboard full of old Avalon Hill titles about 20' from where I'm sitting to write this post and a bookcase of RPG books and other things on the bookcase behind me.
\nPhoto by Gian-Luca on Unsplash
", "image": "https://stephencollins.org/media/posts/8/gian-luca-eubgK-4bzKA-unsplash.jpg", "author": { "name": "Stephen Collins" }, "tags": [ "TTRPG", "Computer games", "Board games" ], "date_published": "2026-05-28T13:32:10+10:00", "date_modified": "2026-05-28T13:34:34+10:00" }, { "id": "https://stephencollins.org/posts/take-in-the-view-take-in-all-the-things-make-notes/", "url": "https://stephencollins.org/posts/take-in-the-view-take-in-all-the-things-make-notes/", "title": "Take in the view. Take in all the things. Make notes.", "summary": "Look, when the feature image for this post is the actual view from my back verandah, it's not all that hard to be…", "content_html": "\n
Look, when the feature image for this post is the actual view from my back verandah, it's not all that hard to be inspired. However, turning that inspiration into at least seeds and perhaps a few cuttings for adventures, is a whole other story when you have 100 acres of bush property to manage, run a B&B, work on a dairy farm, and have a relationship to maintain. So, here's how I manage.
\nI read. A lot. From a wide range of sources. My RSS reader has over 50 feeds in it with topics ranging across reliable news and current affairs, farming, homesteading, design, DIY and maker things, pop culture, smart home, tech, and of course, TTRPGs and other gaming. I use Terry Godier's marvellous Current, which has completely changed the way I consume written material from my feeds. I can work my way through a day's worth of inbound material in about 45 minutes, sending off those I'm not interested in and opening tabs for things I want to read later or reading shorter things immediately. I also read a lot of printed material—books and magazines—and probably spend an hour or so a day after dinner doing this.
\nRight now, I'm reading:
\nI listen to several podcasts regularly, including:
\nI have a growing and heavily tagged Obsidian vault for things that are just about TTRPGs (or things where I can draw a relationship to TTRPGs). I have another vault for saving other material I want to be able to reference. Recent saved notes include:
\nI've been heavily embedded in consuming pop culture since the early 1980s and listen to a lot of different music genres, watch TV across themes such as crime (but avoid copaganda), horror and weird, fantasy, and a lot of documentary and factual. Current watches others might be interested in are:
\nBefore moving to the bush I was a service designer for many years. As part of that career, I developed a very strong capability for systems thinking; understanding that the world is made up of systems of systems means you can identify and comprehend the connections between things in a powerful way that helps to grasp your place in the world. It absolutely helps you to understand how things connect and why. Your curiosity is never sated.
\nManaging a bush property isn't short of inspiration either, and in a little over 5 years living here in the bush, I've learned it's fundamentally different to the life I lived in my first 50 years in cities. The way you have to think about life—chores and maintenance, going to town and how often (it's a 50km round trip for us), the things you really need, what's valuable and brings you joy and what doesn't—are not the same as when everything is close by and easy. On any day, I might be repairing a bit of fence, tidying our garden, cutting firewood from fallen trees, restoring an old tool or fixing a water pump, or building some handy thing from scrap wood (I'm designing a hardwood dice tray at the moment and will start experimenting on cheap timber soon). I also have to build my granddaughter a bookcase!
\nInspiration can come from anywhere and anything. Go looking. Note things down. You never know when something will spark your creativity.
\n![\"RPG](\"https://ofdiceanddragons.com/wp-content/uploads/2017/11/RPGBlogCarnivalLogoSmall.jpg\")
Self-publishing, crowdfunding, and social media publicity underpin the incredibly rich ecosystem of TTRPG material one can purchase in the modern era. You would need a very wealthy benefactor to buy even just the things you are personally interested in.
\nIt's a vastly different world than when I first began playing in the early 1980s when regular visits to the local game store with your hard-earned cash from your weekend job got you the occasional new module or supplement a handful of times a year. Now, there are new things being brought to life every week, from cheap and cheerful lists of 100 new oozes you can have as a familiar to entire mega-funded campaign and rules supplements like Neon Odyssey. We're spoiled for (or paralysed by) choice.
\nSomething I've noticed in many of these works is a reliance on AI tools like Midjourney to produce the visuals that fill them. Given the well-understood and legitimate questions regarding the use of AI, it's a good thing that Kickstarter and other crowdfunding platforms require projects to state whether and how they're using AI tools in their projects. You'll see frequent statements saying things like:
\n\n\nTo enhance the visual appeal of our supplement, we utilize AI tools (such as Midjourney, and Firefly) to generate some of the images. These AI-generated images are then carefully edited by our team to align with the creative vision of our project.
\n
I've purchased a handful of these materials, being interested in the content, but I have had the sense that something was amiss. Sitting back and thinking about what's not right, of course, is the question of whether supporting independent authorship of TTRPG material with my money is moral and ethical when the project has used AI tools to generate some part of the project (usually art, but also other elements such as editing and music)?
\nI’m not going to reprosecute all the extensive arguments for not using AI; those have been made by people far more expert than I. If you want to read a strongly worded summary of those arguments with extensive linking in a single place, you should not go past Anthony Moser’s outstanding essay I am an AI Hater. Moser gets completely to the point when he concludes:
\n\n\nI became a hater by doing precisely those things AI cannot do: reading and understanding human language; thinking and reasoning about ideas; considering the meaning of my words and their context; loving people, making art, living in my body with its flaws and feelings and life. AI cannot be a hater, because AI does not feel, or know, or care. Only humans can be haters. I celebrate my humanity.
\n
Even if the written content of a project is remarkably good, projects choosing to use AI generated art (for every kind of artistry)—often in a particular and recognisable style—present us a dilemma: principally, whose art is this emulating and how was the AI trained to do this?
\nAlongside this core question, do we actually want every new D&D, or Daggerheart, or Mork Borg supplement or module to emulate the original’s art style, or do we want to open up possibilities for new and emerging TTRPG artists, musicians, sound designers, and cartographers to enter the industry? There are literally thousands of people out there—easily found on places from Instagram to DeviantArt—who would gladly join your project and help with artistic assets for a fair share of the profits, or a reasonable fee, and to see their work in print.
\nAlternatively, if your budget really doesn't extend to paying someone to make art for your project (and maybe you should ask yourself why this is the case), the web is literally full of sources for free or low-cost visuals and sounds in just about any style from photographic reality to Victorian illustration line drawings to paintings in the public domain from places like the Rijksmuseum and British Museum.
\n![\"A](\"https://stephencollins.org/media/posts/6/IMG_2724-3.jpeg\")
\nHey, I'm no artist but I'll have a go at maps and they're pretty acceptable. You can certainly make your own. Playing games like Australian micro-studio Ravensridge Emporium's Cartograph will help you build skills in both mapping and writing narrative. They also happen to have taken a hard stance against the use of AI in their products. So too have much larger studios like Kobold Press, who made their commitment almost two years ago.
\n\n\n\n
\n\n
\nThis same argument stands for improving the writing and visual design on TTRPG projects, as it does for the inclusion of thematic or mood sound, effects, and music. Go find an editor, musician, or layout designer and ask them to help improve your material for a reasonable fee before you fling the project onto Kickstarter or Backerkit.
\nFrom now on, I’m going to do two things:
\nIn conclusion, I'd like to encourage you to consider where you stand on the use of AI in TTRPG design. I'm not here to tell you what decision you should make, but I would ask that next time you're about to back a project that chooses to use AI for parts of its development process that you ask yourself whether that's an ethical or morally sound decision given all the factors at play.
", "image": "https://stephencollins.org/media/posts/6/marija-zaric-AXL7xerPCUU-unsplash.jpg", "author": { "name": "Stephen Collins" }, "tags": [ "TTRPG", "Ethics", "Design", "AI" ], "date_published": "2026-05-22T10:10:04+10:00", "date_modified": "2026-05-22T16:48:19+10:00" }, { "id": "https://stephencollins.org/posts/welcome-to-the-valley/", "url": "https://stephencollins.org/posts/welcome-to-the-valley/", "title": "Welcome to the Valley!", "summary": "It me! Hello, there! I'm Stephen Collins. You can read more about me over here. Long ago, I wrote a blog about design…", "content_html": "![\"Stephen](\"https://stephencollins.org/media/posts/3/330317813_153944870865598_7317854811952586013_n.jpg\")
\nHello, there! I'm Stephen Collins. You can read more about me over here.
\nLong ago, I wrote a blog about design thinking, organisational and service design, running a business, and my perspectives on leadership. You can probably still find a lot of it on archive.org or Medium if you go looking.
\nI've wanted to blog again for a while, and write about things like living in the bush and how it differs from the city life I spent my first 50ish years living; being a maker, maintainer, and repairer of things; the books, games, and music I encounter; and not least of all a place to write about interesting and useful material for your 5e tabletop roleplaying games.
\n![\"Human](\"https://stephencollins.org/media/posts/3/5_circle_text_with_hand.png\")
I live in a place called Brogo, which is a hundred-or-so square kilometres of farmland and native bush about 25km from Bega on the far south coast of New South Wales.
\n![\"An](\"https://stephencollins.org/media/posts/3/Where.png\")
\nThat puts us 25km from the nearest town of Bega, 3 hours from the national capital, Canberra (and the nearest game store), 5 hours from Sydney, and about 9 hours from Melbourne.
\nIRL I run a sustainably-managed, dog-friendly B&B on 100 acres in the hills of the Bega Valley (NSW, Australia), which is Djiringanj Yuin country for our First Nations people. I work on a large dairy farm. I'm (mostly) retired from 20+ years of working in design of user experience, services, and organisations.
\nI'm an outdoorsman, a bowhunter, a console, board, and TTRPG gamer, a democratic socialist, a husband, a (grand)dad, a DIY/Maker, a volunteer RFS firefighter, a 🐈 and 🐕 dad.
\nMy pronouns are he/him, but whatever works at the time will never bother me.
\nHuman Made logo by Hinokodo
", "image": "https://stephencollins.org/media/posts/3/IMG_2771.jpeg", "author": { "name": "Stephen Collins" }, "tags": [ "Site related", "Personal" ], "date_published": "2026-05-12T12:29:01+10:00", "date_modified": "2026-05-23T12:16:32+10:00" } ] }