Environment

Some environments refer to the rules for climate and natural disasters. Many places have the traits of multiple environments; a snow-covered mountain might use both the arctic and mountain environments, for example. For environmental features with effects based on how tall or deep they are, those effects vary further based on a creature’s size. For instance, a shallow bog for a Medium creature might be a deep bog for smaller creatures, and a deep bog for a Medium creature could be only a shallow bog for a larger creature (and so insignificant for a truly massive creature that it isn’t even difficult terrain).

Environmental Damage

Some environmental features or natural disasters deal damage. Because the amount of damage can vary based on the specific circumstances, the rules for specific environments and natural disasters use damage categories to describe the damage, rather than exact numbers. Use the table below to determine damage from an environment or natural disaster. When deciding the exact damage amount, use your best judgment based on how extreme you deem the danger to be.

Environmental Damage

Category	Damage
Minor	1d6-2d6
Moderate	4d6-6d6
Major	8d6-12d6
Massive	16d6-24d6

Aquatic

Aquatic environments are among the most challenging for PCs short of other worlds and unusual planes. PCs in an aquatic environment need a way to breathe (typically a water breathing spell) and must usually Swim to move, though a PC who sinks to the bottom can walk awkwardly, using the rules for greater difficult terrain. Characters in aquatic environments make frequent use of the aquatic combat and drowning and suffocation rules.

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Drowning and Suffocation

You can hold your breath for a number of rounds equal to 5 + your Constitution modifier. Reduce your remaining air by 1 round at the end of each of your turns, or by 2 if you attacked or cast any spells that turn. You also lose 1 round worth of air each time you are critically hit or critically fail a save against a damaging effect. If you speak (including casting spells with verbal components or activating items with command components) you lose all remaining air.

When you run out of air, you fall unconscious and start suffocating. You can’t recover from being unconscious and must attempt a DC 20 Fortitude save at the end of each of your turns. On a failure, you take 1d10 damage, and on a critical failure, you die. On each check after the first, the DC increases by 5 and the damage by 1d10; these increases are cumulative. Once your access to air is restored, you stop suffocating and are no longer unconscious (unless you’re at 0 Hit Points).

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Currents and Flowing Water

Ocean currents, flowing rivers, and similar moving water are difficult terrain or greater difficult terrain (depending on the speed of the water) for a creature Swimming against the current. At the end of a creature’s turn, it moves a certain distance depending on the current’s speed. For instance, a 10-foot current moves a creature 10 feet in the current’s direction at the end of that creature’s turn.

Visibility

It’s much harder to see things at a distance underwater than it is on land, and it’s particularly difficult if the water is murky or full of particles. In pure water, the maximum visual range is roughly 240 feet to see a small object, and in murky water, visibility can be reduced to only 10 feet or even less.

Arctic

The main challenge in an arctic environment is the low temperature, but arctic environments also contain ice and snow. The disasters that most often strike in arctic environments are avalanches, blizzards, and floods.

Ice

Icy ground is both uneven ground and difficult terrain, as characters slip and slide due to poor traction.

Snow

Depending on the depth of snow and its composition, most snowy ground is either difficult terrain or greater difficult terrain. In denser snow, characters can attempt to walk along the surface without breaking through, but some patches might be loose or soft enough that they’re uneven ground.

Desert

Desert encompasses sandy and rocky deserts as well as badlands. Though tundra is technically a desert, it’s classified as arctic, as the climate is the primary challenge in such areas. Sandy deserts often have quicksand hazards and sandstorms.

Rubble

Rocky deserts are strewn with rubble, which is difficult terrain. Rubble dense enough to be walked over rather than navigated through is uneven ground.

Sand

Packed sand doesn’t usually significantly impede a character’s movement, but loose sand is either difficult terrain (if it’s shallow) or uneven ground (if it’s deep). The wind in a desert often shifts sand into dunes, hills of loose sand with uneven ground facing the wind and steeper inclines away from the wind.

Forest

These diverse environments include jungles and other wooded areas. They are sometimes struck by wildfires.

Canopies

Particularly dense forests, such as rain forests, have a canopy level above the ground. A creature trying to reach the canopy or travel along it must Climb. Swinging on vines and branches usually requires an Acrobatics or Athletics check. A canopy provides cover, and a thicker one can prevent creatures in the canopy from seeing those on the ground, and vice versa.

Trees

While trees are omnipresent in a forest, they typically don’t provide cover unless a character uses the Take Cover action. Only larger trees that take up an entire 5-foot square on the map (or more) are big enough to provide cover automatically.

Undergrowth

Light undergrowth is difficult terrain that allows a character to Take Cover. Heavy undergrowth is greater difficult terrain that automatically provides cover. Some sorts of undergrowth, such as thorns, might also be hazardous terrain, and areas with plenty of twisting roots might be uneven ground.

Mountain

Mountain environments also include hills, which share many aspects of mountains, though not their more extreme features. The most common disasters here are avalanches.

Rubble

Mountains often have extremely rocky areas or shifting, gravelly scree that makes for difficult terrain. Especially deep or pervasive rubble is uneven ground.

Slopes

Slopes vary from the gentle rises of normal terrain to difficult terrain and inclines, depending on the angle of elevation. Moving down a slope is typically normal terrain, but characters might need to Climb up particularly steep slopes.

Undergrowth

Light undergrowth is common in mountains. It is difficult terrain and allows a character to Take Cover.

Plains

The plains environment encompasses grasslands such as savannas and farmland. The most common disasters in plains are tornadoes and wildfires.

Hedges

Hedges are planted rows of bushes, shrubs, and trees. Their iconic appearance in adventures consists of tall hedges grown into mazes. A typical hedge is 2 to 5 feet tall, takes up a row of squares, and provides cover. A character trying to push through a hedge faces greater difficult terrain; it’s sometimes faster to Climb over.

Undergrowth

Light undergrowth is difficult terrain that allows a character to Take Cover. Heavy undergrowth is greater difficult terrain that provides cover automatically. Undergrowth in plains is usually light with a few scattered areas of heavy undergrowth, but fields of certain crops, like corn, are entirely heavy undergrowth.

Swamp

Wetlands are the most common kind of swamp, but this category also includes drier marshes such as moors. Swamps often contain quicksand hazards. Despite their soggy nature, swamps aren’t very likely to experience heavy flooding, since they act as natural sponges and absorb a great deal of water before they flood.

Bogs

Also called mires, bogs are watery areas that accumulate peat, are covered by shrubs and moss, and sometimes feature floating islands of vegetation covering deeper pools. Shallow bogs are difficult terrain for a Medium creature, and deep bogs are greater difficult terrain. If a bog is deep enough that a creature can’t reach the bottom, the creature has to Swim. Bogs are also acidic, so particularly extreme or magical bogs can be hazardous terrain.

Undergrowth

Light undergrowth is difficult terrain that allows a character to Take Cover, while heavy undergrowth is greater difficult terrain that provides cover automatically. Some sorts of undergrowth, such as thorns, are also hazardous terrain, and areas with plenty of twisting roots are uneven ground.

Urban

Urban environments include open city spaces as well as buildings. The building information in this section also applies to ruins and constructed dungeons. Depending on their construction and location, cities might be vulnerable to many sorts of disasters, especially fires and floods.

Crowds

Crowded thoroughfares and similar areas are difficult terrain, or greater difficult terrain if an area is truly packed with people. You might allow a character to get a crowd to part using Diplomacy, Intimidation, or Performance.

A crowd exposed to an obvious danger, like a fire or a rampaging monster, attempts to move away from the danger as quickly as possible, but it is slowed by its own mass. A fleeing crowd typically moves at the Speed of an average member each round (usually 25 feet), potentially trampling or leaving behind slower-moving members of the crowd.

Doors

Opening an unlocked door requires an Interact action (or more than one for a particularly complicated or large door). Stuck doors must be Forced Open, and locked ones require a character to Pick the Lock or Force them Open.

Door	Climb DC	Hardness, HP (BT)
Wood	20	10, 40 (20)
Stone	30	14, 56 (28)
Reinforced wood	15	15, 60 (30)
Iron	30	18, 72 (36)

Floors

Wooden floors are easy to walk on, as are flagstone floors made of fitted stones. However, floors of worn flagstone often contain areas of uneven ground.

Gates

Walled settlements often have gates that the city can close for defense or open to allow travel. A typical gate consists of one portcullis at each end of a gatehouse, with murder holes in between or other protected spots from which guards can attack foes. Use the same DCs, Hardness, Hit Points, and Break Thresholds as Doors above.

Guards

Most settlements of significant size have guards working in shifts to protect the settlement at all hours, patrolling the streets and guarding various posts. The size of this force varies from one guard for every 1,000 residents to a force 10 times this number.

Portcullises

A portcullis is a wooden or iron grate that descends to seal off a gate or corridor. Most are raised on ropes or chains operated by a winch, and they have locking mechanisms that keep them from being lifted easily. The rules on lifting a portcullis or bending its bars appear below. If a portcullis falls on a creature, use a slamming door trap.

Portcullis	Climb DC	Hardness, HP (BT)	Lift/Bend Bars DC
Wood	10	10, 40 (20)	20
Iron	10	18, 72 (36)	30

Rooftops

Rooftops make for memorable ambushes, chase scenes, infiltrations, and running fights. Flat roofs are easy to move across, but they’re rare in any settlement that receives significant snowfall, since heavy buildups of snow can collapse a roof. Angled roofs are uneven ground, or inclines if they’re especially steep. The peak of an angled roof is a narrow surface.

Hurdling from roof to roof often requires a Long Jump, though some buildings are close enough to Leap between. A High Jump might be necessary to reach a higher roof, or a Leap followed by Grabbing an Edge and Climbing up.

Sewers

Sewers are generally 10 feet or more below street level and are equipped with ladders or other means to ascend and descend. Raised paths along the walls allow sewer workers access, while channels in the center carry the waste itself. Less sophisticated sewers, or sections those workers don’t usually access, might require wading through disease-ridden waste. Sewers can be accessed through sewer grates, which usually require 2 or more Interact actions to open.

Sewer Gas

Sewer gas often contains pockets of highly flammable gas. A pocket of sewer gas exposed to a source of flame explodes, dealing moderate environmental fire damage to creatures in the area.

Stairs

Stairs are difficult terrain for characters moving up them, and shoddy stairs might also be uneven ground. Some temples and giant-built structures have enormous stairs that are greater difficult terrain both up and down, or might require Climbing every step.

Walls

Well-built structures have exterior walls of brick or stonemasonry. Smaller, lower-quality, or temporary structures might have wooden walls. Interior walls tend to be less sturdy; they could be made of wooden planks, or even simply of thick, opaque paper held in a wooden frame. An underground structure might have thick walls carved out of solid rock to prevent the weight of the ground above from collapsing the structure.

Wall	Climb DC	Hardness, HP (BT)
Crumbling masonry	15	10, 40 (20)
Wooden slats	15	10, 40 (20)
Masonry	20	14, 56 (28)
Hewn stone	30	14, 56 (28)
Iron	40	18, 72 (36)

Underground

Underground environments consist of caves and natural underground areas. Artificial dungeons and ruins combine underground features with urban features like stairs and walls. Deep underground vaults have some of the same terrain features as mountains, such as chasms and cliffs. The most common disasters underground are collapses.

Floors

Natural underground environments rarely have flat floors, instead featuring abrupt changes in elevation that result in difficult terrain, uneven ground, and inclines.

Ledges

Ledges are narrow surfaces that overlook a lower area or provide the only means to move along the edge of a chasm. Moving across a narrow ledge requires using Acrobatics to Balance.

Rubble

Caverns can be covered in rubble, which is difficult terrain. Deep or pervasive rubble is also uneven ground.

Stalagmites and Stalactites

Stalagmites are tapering columns that rise from the floor of a cave. Areas filled with stalagmites are greater difficult terrain, and especially large stalagmites have to be sidestepped or Climbed. Stalagmites can be sharp enough they can be used as hazardous terrain in some circumstances, as can stalactites (icicle-shaped formations that hang from the roof of a cave) if they’re knocked loose from a ceiling or overhang.

Walls

Natural cave walls are uneven, with nooks, crannies, and ledges. Since most caves are formed by water, cave walls are often damp, making them even more difficult to Climb.