The following rules cover environmental hazards one may end up encountering.
While inside of acid, anyone who isn’t immune starts to take damage due to the acid burning and eating the skin of its target. Those inside of the acid take 2 acid damage bypassing Soak per round of being in the acid. Being totally submerged in acid deals 8 acid damage bypassing Soak per round to the one being submerged, and the target may suffer from drowning.
In addition to all of this, while adjacent to acid the fumes deal damage to one’s lungs. Anyone near the acid without proper gear has an attack made against Bodily Defense (4k2 Attack, +1k1 for every minute spent in the area) and on a successful hit the character is nauseated.
Planets have varying atmospheres beyond the normal, breathable and sustainable ones. Some are more dangerous than others. Usually space suits or similar worn materials are used to combat these.
Corrosive: Corrosive atmospheres eat away at clothing, flesh, and even some metals. Those who begin their turn unprotected in corrosive atmospheres take a 5k2 attack (increasing by +1k1 on subsequent rounds in the atmosphere) to their Bodily Defense. On a successful hit, they take 2 points of damage bypassing Soak (or half on a miss).
Toxic: Toxic atmospheres have chemicals that harm living beings, and sometimes rust machinery. Those who begin their turn unprotected in toxic atmospheres take a 6k3 attack (increasing by +1k1 on subsequent rounds in the atmosphere) to their Bodily Defense. On a successful hit, they take 2 points of damage bypassing Soak (or half on a miss) and become nauseated.
Avalanches tend to occur on mountainsides and when a weapon or object makes a loud noise that causes it to come tumbling down. The GM decides the size and speed of an avalanche however it usually moves at a 4 square speed and is between 10x10 to 20x20 squares large. Avalanches have an 8k6 vs. their target's Avoid, and on a successful hit deals 8 points of bludgeoning damage bypassing Soak. On a miss the damage is halved. If the avalanche beats their Avoid by 5 or more they are buried under in the avalanche and must make a DC 30 Acrobatics check to crawl out, or an ally must spend 1 minute or more of digging to pull them out of being buried. Being buried can potentially lead to suffocation if they're stuck in there too long.
Rock slides function the same as an avalanche, yet deal 6 bludgeoning damage bypassing Soak instead.
Being in boiling water deals 2 points of water and fire damage bypassing Soak, and being fully submerged in the boiling water deals 6 points of water and fire damage bypassing Soak. Characters who are submerged are at risk of drowning.
Creatures and even building and objects inside of a blizzard all receive concealment. In addition, they have an attack made against their Bodily Defense starting at 5k3 and increasing by +1k1 for every hour they remain in the blizzard. On a successful hit they take 1 point of ice damage bypassing Soak and 11 point of bludgeoning damage bypassing Soak. On a miss they take one or the other, not both. A successful DC 26 Fortitude check after the first attack roll is made grants the creature a +5 bonus to their Bodily Defense against the next attack roll by the blizzard.
Sandstorms function the same way, except they take 2 points of bludgeoning damage (1 on a miss).
When fire reaches a character’s hair, clothing, or other flammable materials on the character they have a chance of catching on fire. A character at risk of catching on fire has an attack made against their Avoid (5k3 Attack) and on a success they start taking 1 fire damage per round bypassing Soak. A fire can be doused by at least a water skin.
If a character takes half their HP or more in fire damage while having been caught on fire, they receive an attack against their Bodily Defense (7k3 Attack) and on a success their eyes melt, and they are blinded until magical healing that restores blindness is cast.
A cave-in has an attack of 8k4 vs. Avoid, and on a successful hit those within the cave-in take 4 points of bludgeoning damage bypassing Soak (half damage on a miss). If the cave-in beats their Avoid by 5 or more they are buried under in the avalanche and must make a DC 30 Acrobatics check to crawl out, or an ally must spend 1 minute or more of digging to pull them out of being buried. Being buried can potentially lead to suffocation if they're stuck in there too long.
A character can hold their breath under water for a number of rounds equal to twice their Endurance. If a character takes a standard or full-round action, the remaining duration they can hold their breath for is reduced by 1. After this, they must make a DC 10 Fortitude check in order to continue holding their breath. The check must be repeated each round, with the DC increasing by +2 for each previous save.
When the character fails their Fortitude check, they begin to drown. In the first round, they fall unconscious at 0 HP. In the following round, they drop to -1 HP and are dying. In the third round they drown to death. It is possible to drown in substances other than water such as; quicksand, lava, and acid.
A huge whirlwind that rages through the sands, any creature within 3 squares of the dust devil (typically counting as medium or large size) have an attack made against their Avoid, this attack being made at a 4k2 and increasing by +1k1 for every square closer to the dust devil the creature is. On a successful hit they take 1 point of nonlethal bludgeoning damage bypassing Soak (half on a miss) and if the attack bypasses their Avoid by 5 or more they are sucked into the whirlwind and tossed 1d5 squares away in a random direction of the GM's choice. Upon lading they take an additional 1 point of nonlethal bludgeoning damage bypassing Soak.
Creatures touching an electric fence have an attack of 6k4 made against their Avoid (or 10k5 if they are pressed against the fence), and take 1 points of electricity damage bypassing Soak. On a miss they take half damage. If they are pressed against the fence, they instead take 2 points of damage bypassing Soak and are stunned for 1 round.
A high voltage fence deals 3 points of electricity damage bypassing Soak (6 for being pressed against the fence).
When a plasma conduit behind a character is intentionally shot (or hit due to GM determining a missed attack hits it), superheated plasma pours out with an attack roll of 7k4 vs. the target's Avoid, dealing 2 points of fire and electricity damage bypassing Soak to all adjacent squares. On a miss this deals half damage. This plasma spill deals continuous damage to the surroundings and any creatures within it for 1d10+4 rounds.
Sometimes characters can be launched in the air or fall from large distances. If a character falls a certain number of feet, they will suffer falling damage on the following round of falling. In addition to this, they’ll take damage if they hit walls, ceilings, and other hard surfaces instead of landing on the ground.
For every 2 squares a character falls from, they take 1 point of damage bypassing Soak (considered bludgeoning normally, spiked pits are piercing/slashing). The maximum amount of damage a character can take is 20 at 40 sq. after which the damage is instantly lethal and will kill the person falling upon impact unless they have a way to stop this damage. Deflection doesn't factor into fall damage. At the end of a fall, the person who fell is prone.
Objects of certain sizes which fall and land upon someone take damage bypassing Soak. The object can be debris from a collapsing building, or the remains of a spaceship colliding with the planet it is trying to reenter. Regardless of the circumstance, the damage is listed here. Objects listed with a † are instantly lethal and kill upon impact.
Attacks which miss a character only deal half damage instead.
Lava or magma deals 3 points of fire damage bypassing Soak per round while being exposed, unless the character is completely submerged, in which case they take 8 points of fire damage per round. Immunity to fire is also immunity to lava and magma.
Damage lasts for 1d5 rounds after exposure, but the damage dealt is halved. Characters who are immune to lava/magma/fire may still drown if completely submerged for too long.
When a creature begins its turn in an area of sand that isn't very tightly packed, it is considered difficult terrain. In addition for every square they move within the loose sand they have an attack roll of 4k2 made against their Avoid (an additional +1k1 is added on for every square beyond the first during that round) and on a successful hit they stop in that square and are only able to take a move action for the rest of their turn.
Quicksand follows similar rules to loose sand, except that on a successful hit they instead are stopped in that square and begin to sink. The creature first sinks to their waist, and are reduced to half speed (in addition to the reduction from difficult terrain) and receive attack rolls of 5k3 to their Avoid for each square they move (an additional +2k0 is added on for every square beyond the first during that round). On a successful hit, they stop moving and sink down to their chest. At this point they are completely immobilized and considered helpless. On the round after, they begin to drown in the quicksand.
When running through areas of low-hanging branches, an attack of 4k2 is made against their Avoid (+1k1 for every square they move through that is also considered low-hanging branches) and those hit take 1 points of slashing bypassing Soak damage. While mounted they instead take 2 points of slashing damage.
Opening and closing at random intervals, this automatic door has an attack of 4k2 vs. Avoid and deals 2 points of bludgeoning damage bypassing Soak on a successful hit (and dealing no damage on a miss).
Any creature ending its turn adjacent to the pit or sinkhole has an attack of 4k2 made against their Avoid, and on a successful hit they fall into the hole taking falling damage appropriate to how far down the character falls. Every subsequent round the attack roll increases by +1k1.
These masses of psychic energy are harmful for those within it, and have an attack of 7k3 made against their Mental Defense. On a successful hit they take 1 points of psychokinetic damage bypassing Soak and are confused for 1 round. This effect is hourly. If the person is immune to mind-affecting effects, they're immune to this effect.
A character who breathes in heavy smoke has an attack made against their Bodily Defense (4k2 Attack, +1k1 per previous check made) and on a success they spend the turn coughing and choking. A character who chokes for 2 consecutive rounds take 1 nonlethal damage bypassing Soak per round of choking thereafter. Smoke conceals vision, imposing a 20% miss chance.
A character can go 1 day without water + 1 additional day per Endurance. After this time, the character must pass a Fortitude check (DC 10, +2 per previous check made) each hour and on a failed check they take 1 nonlethal damage (bypassing Soak). Characters brought to 0 HP this way start taking lethal damage instead.
A character can go without food for 3 days in growing discomfort. After this time, the character must pass a Fortitude check (DC 10, +2 per previous check made) each day and on a success they take 1 nonlethal damage (bypassing Soak). A character brought to 0 HP this way start taking lethal damage instead.
Storms of holy or unholy energy rage in certain areas where these energies are prevalent. Rather than affecting creatures physically, they affect them spiritually. An attack of 6k4 is made against the Mental Defense of those in the storm, and on a successful hit they take 2 points of damage bypassing Soak appropriate for the type of storm (holy or unholy). This effect is hourly.
A character who has no air to breathe can hold their breath for 2 rounds per Endurance. If a standard or full-round action is taken, the character loses 1 round that they can hold their breath for. After this, they must make a DC 10 Fortitude check in order to continue holding their breath. The check must be repeated each round, with the DC increasing by +1 for each previous save.
When a character fails one of these Fortitude checks, they begin to suffocate. In the first round, they fall unconscious at 0 HP. In the following round, they drop to -1 HP and are dying. In the third round they suffocate to death.
Being in the same square as a large thornbush harms those inside. An attack of 4k2 is made against their Defense for every round creatures remain within it, and they take 1 points of slashing or piercing damage bypassing Soak on a successful hit (a miss deals half damage). A thornbush can be sliced through with slashing weapons, or burnt through with fire weapons. Thornbushes are considered to have 10 HP for the sake of this, and increase their HP by 10 for every size category they are considered beyond a regular human’s size of 1 square.
Vehicles moving down a highway have a chance of striking those who enter into the freeway. An attack roll of 6k3 vs. Avoid is made against anyone beginning their turn in the area of traffic. On a successful attack they take 3 points of bludgeoning damage bypassing Soak, and on a miss they take 1 point of bludgeoning damage bypassing Soak as they're sideswiped by a vehicle. This area is considered difficult terrain.
When a creature begins its turn in a vacuum environment (such as the vacuum of space) and doesn't have ample survival gear for breathing in space, they receive an attack against their Bodily Defense (this attack is made at a 10k8, and increases by +1k1 for every subsequent round) and on a successful hit the target takes 2 points of damage bypassing Soak. Every round thereafter the damage increases by +1. If the damage brings them to 0, they die due to explosive decompression. In addition to the damage, characters in the vacuum are considered to be suffocating.
If a creature or vehicle enters into the square of a whirlpool while in the water, they start getting sucked into the center of the whirlpool. This is a 4k4 attack vs. the target's Avoid (increasing by +1k1 for every subsequent round in the whirlpool) and on a successful hit the target takes 1 point of bludgeoning damage bypassing Soak and is moved 3 squares of the GM's choice (usually nearing the center with 1 of these squares). On a miss, the target doesn't take any damage and is moved 1 square of the GM's choice. This area is considered difficult terrain for the purpose of movement.