Ah, lava. The ultimate expression of nature’s destructive power. The awesome force of annihilation that is the antithesis to the equally amazing force of life. The doom of thousands throughout history. The peril that every fantasy in the history of fantasy utterly fails to represent in any manner close to realism.
In this article, we will look at the science of lava and why it is such a dangerous hazard to use in your game. We will also provide recommendations for how to avoid downplaying the dangers associated with it and, hopefully, encourage your players to not tempt their chances at this article’s name.
Let’s first establish some terminology. Magma is molten rock that lies beneath the Earth’s surface. Lava is magma that has been forced above the surface where it rapidly cools. The two terms refer to the same substance in popular culture, and so throughout this article we will use ‘lava’, except where it is specifically understood to be in reference to underground molten rock.
How Hot Is Lava?
Lava is hot. We mean, really hot. Lava flows can get as high as 1,600°F, while magma can reach 2,120°F. For comparison, skin burns in under a second at 160°F (you will suffer third degree burns after two seconds immersed in 150°F water). The highest survived internal body temperature was 115°F.
Now, we’re talking about molten lava here. By that, we mean the bright stuff, not the cooler crust that forms atop slow-moving lava flows as the heat radiates out and the rock returns to a more solid state. Lava with such a ‘skin’ is probably closer to 500°F, and the only person in history to ever have fallen into lava and survived had the dubious fortune to have fallen into such a flow. This state of lava, being something which a particularly lethargic turtle could outrun, is virtually never encountered in adventures, which favour the dramatic over the realistic, and so we are not going to bother discussing it in this article. What we are talking about in this article are bright, orange flows—the stuff of epic fantasy.
There are a few important factors to consider when approaching lava.
- The angle of exposure (“How much lava do you see?”)
- The temperature of the lava
- Air flow
- The reflectiveness of what you’re wearing
- Toxic fumes
Let’s set aside the fact that the hydrogen sulphide gasses from a volcanic flow are likely to kill you before you can fall into the lava itself and just focus on the heat. (As much as we like to be realistic, we realize that the toxic fumes are not why you’re here. You want to know how hot it gets so you can make an informed decision about the damage to roll, so let’s get to it.)
The heat flux from an object (in this case, a lava flow) drops as the square of distance, so as you get closer and closer it will get exponentially hotter. At a distance of 94 million miles, the intensity of the sun’s light on Earth is one thousand watts (1 kilowatt) per square metre, or 1 kW/m². For a typical lava flow (say 1,300°F), you would experience the same heat by approaching with 30 feet at a 10 degree angle to the lava, and an average (5’9”) person who approaches within 6 feet of lava at just a 50 degree angle will be feeling the heat of 25 suns directly on their face.
So, when designing encounters that include lava, be sure to deal fire damage to players stupid enough to approach within 30 feet of it. And, when placing bridges over lava, don’t place them at a height of only 5 feet (like Wizards of the Coast has done on numerous occasions…). At least, not if you don’t want your PCs to instantly suffer severe burns. To make it simple, here are our very simplistic suggestions:
- Within 30 feet of lava, a creature takes 1d4 fire damage per round. Even at this distance, the skin becomes visibly flushed with exposure. Unless you have fire resistance, the heat causes your eyes to water, imposing disadvantage on attack rolls and Wisdom (Perception) checks based on sight. At the beginning of every round that the creature is exposed to the lava, they must succeed a DC 10 Constitution saving throw or suffer 1 level of exhaustion. These effects are negated if the character ducks down or avoids exposing themselves to the lava.
- Within 20 feet of lava, a creature takes 1d10 fire damage per round unless they crouch down (half movement speed). Exposed skin suffers second-degree burns that take 2d6 days to heal without magical healing. At the beginning of every round that the creature is exposed to the lava, they must succeed a DC 15 Constitution saving throw or suffer 1 level of exhaustion. Creatures wearing medium or heavy armour, or who are clad in heavy clothing, have disadvantage on the saving throw. Creatures with resistance or immunity to fire damage automatically succeed on the saving throw.
- Within 10 feet of lava, a creature takes 4d10 fire damage per round unless they crouch down (half movement speed). Exposed skin suffers second-degree burns that take 3d6 days to heal without magical healing. At the beginning of every round that the creature is exposed to the lava, they must succeed a DC 20 Constitution saving throw or suffer 1 level of exhaustion. If the creature was not holding their breath, is wearing medium or heavy armour, or is clad in heavy clothing, they have disadvantage on the saving throw. Creatures with resistance or immunity to fire damage automatically succeed on the saving throw.
- Within 5 feet of lava, a creature takes 20d10 fire damage per round, or half as much if they lie prone (they can crawl 10 feet per round). Under direct exposure, cloth garments burn away, metal armour sears to flesh, and exposed skin suffers third-degree burns, causing permanent disfigurement to exposed extremities. The DM determines the nature of this disfigurement (the Lingering Injuries table in the Dungeon Master’s Guide has some great suggestions). At the beginning of every round that the creature is exposed to the lava, they must make a DC 25 Constitution saving throw. On a success, they suffer 1 level of exhaustion. On a fail, they are reduced to 0 hit points. If the creature was not holding their breath, is wearing medium or heavy armour, or is clad in heavy clothing, they have disadvantage on the saving throw. Creatures with immunity (but not resistance) to fire damage automatically succeed on the saving throw.
There idea of a ‘safe’ distance to cross over lava is really somewhat paradoxical, not only because heat rises but also because molten magma can bubble, creating jets that spray up dozens of feet. Nonetheless, creatures with resistance or immunity to fire may build their homes in proximity to molten magma, which may require building bridges or platforms above the flows that can provide for an impressive setting for a fight scene.
With sufficient air flow, an adventurer could possibly survive crossing a bridge sufficiently high above magma, especially if it is a stone bridge with solid side-guards that offer some protection from the direct heat. When designing dungeons that adventurers could survive, we suggest placing such bridges at heights of at least 60 feet (if the bridge is exposed to open air that cools the surrounds) or 90 feet (if the bridge is located in an enclosed cavern). If the structures would take adventurers closer, we suggest using the same guidelines laid out above, doubling the distance at which damage scales (if in open air) or tripling the distance at which damage scales (if in an enclosed cavern). For example, an open-air bridge within 60 feet of the lava flow or a bridge in a cavern that is within 90 feet of a lava flow would result in the adventurer suffering 1d4 fire damage per round.
Falling Into Lava
At last, we come to the question that most likely brought you here: what happens if you fall into lava?
Now, this section should be prefaced with the caveat that nobody actually knows for sure. This is, rather understandably, not a very well-studied occurrence. It’s hard to get people interested in an experiment in which they will most likely suffer grievous personal injury, if not simply being outright incinerated. Because of a lack of volunteer lava swimmers, much of what we understand of the effects of sudden, intense heat is either from those few eyewitness accounts to the heat wave of nuclear attacks such as at Hiroshima and Nagasaki, or from examining the remains of pyroclastic flow victims, such as those entombed in volcanic ash at Herculaneum and Pompeii. Additionally, physics being what they are, we can make several educated guesses to supplement the existing research.
First of all, let’s be absolutely clear about something that the Dungeon Master’s Guide has lied to you about for years: if you do not have immunity to fire and you fall into lava, you’re just dead. No death saves, no damage rolls, just instant death. Good bye. Only true resurrection or a wish spell can bring you back now. Don’t believe me? Well, fortunately, I am prepared to guide you through the macabre details of what we understand would occur.
For starters, you wouldn’t fall into lava, you would fall onto lava. Lava is molten rock, three times denser than water and at least 100,000 times as viscous; unless you were falling from a great height, the lava would deform under your weight, but you wouldn’t break the surface. If you were to somehow stay there for a while, you might eventually be subsumed by the molten rock. Unfortunately, you would be much too busy being vaporized for this to happen. No, I don’t mean that in a hyperbolic sense.
Have you ever seen a drop of water fall on a hot skillet? Have you seen how it steams, dances, and sizzles? This is called the Leidenfrost Effect, and that drop of water would be you. Your skin would rupture, blacken, and evaporate (going from solid to liquid to gas) so quickly that it would actually cushion your impact against the lava before scattering you across the walls of whatever lava tube or channel you’ve fallen into. Pieces of you would fly in different directions before incinerating into ash.
And if that weren’t enough, as you are destroyed from the outside, you’d be getting destroyed from the inside, as well. Your body, which is made of 60% water (an excellent thermal conductor), would literally boil inside. Your organs would rupture, your bones would crack, your blood would turn to gas inside your veins. Just for good measure, your brain would probably boil so quickly that the pressure would blow your skull apart.
See what I mean when I say “you’re just dead”? There is no quantity of dice to approximate how dead you are at this point. The answer is simply, “Yes”.
Lava is by far one of the most dangerous perils an adventurer will ever encounter, more deadly even than the breath of an ancient red dragon. In spite of this, every official adventure invariably downplays the risk it poses. Whether by giving you grated metal bridges to cross a whole 5 feet above the lava flow (Tomb of Annihilation) or suggesting a mere 6d10 damage for wading into molten magma (Princes of the Apocalypse), it is almost as if Wizards of the Coast (or any movie director in the history of Hollywood movies that inspire them) has never attempted to learn anything about this deadly hazard. In point of fact, both of the situations described above would spell instant, gruesome death for anyone who doesn’t have immunity to fire damage. Lava. Is. Deadly.
The next time you want to include lava in your campaign, try putting your head into your oven when it’s turned up to 400°F. Now imagine if your oven was five times hotter. That’s the hazard you’re throwing at your PCs. It’s not ‘very hot water’ that can be easily waded through, it’s ‘molten death’. Try to impart that to your players. Tell them that, even from dozens of feet away, their characters are being overwhelmed by the heat. Make it a frightening experience, sell them on the danger. They will appreciate the encounter all the more for it. And if they fall in… well, they won’t ever make that mistake again.
Have you ever used lava in an encounter? Did you follow the suggestions of the rules, or did you play it straight? Let us know below!
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