This section describes a few examples of hazards that adventurers might encounter in the wilderness.
Some hazards, such as slippery ice and razorvine, require no ability check to spot. Others, such as defiled ground, are undetectable by normal senses.
The other hazards presented here can be identified with a successful Intelligence (Nature) check. Use the guidelines in d20 Test Section to set an appropriate DC for any check made to spot or recognize a hazard.
Aside from the specific examples listed below, spell effects can be used as a quick and dirty resource to emulate various natural phenomena. See Spell Equivalents of Natural Hazards for more information.
A typical avalanche (or rockslide) is 300 feet wide, 150 feet long, and 30 feet thick. Creatures in the path of an avalanche can avoid it or escape it if they're close to its edge, but outrunning one is almost impossible.
When an avalanche occurs, all nearby creatures must roll initiative. Twice each round, on initiative counts 10 and 0, the avalanche travels 300 feet until it can travel no more. When an avalanche moves, any creature in its space moves along with it and falls prone, and the creature must make a DC 15 Strength saving throw, taking 1d10 bludgeoning damage on a failed save, or half as much damage on a successful one.
When an avalanche stops, the snow and other debris settle and bury creatures. A creature buried in this way is blinded and restrained, and it has total cover. The creature gains 1 level of exhaustion for every 5 minutes it spends buried. It can try to dig itself free as an action, breaking the surface and ending the blinded and restrained conditions on itself with a successful DC 15 Strength (Athletics) check. A creature that fails this check three times can't attempt to dig itself out again.
A creature that is not restrained or incapacitated can spend 1 minute freeing a buried creature. Once free, that creature is no longer blinded or restrained by the avalanche.
A creature can be immersed in frigid water for a number of minutes equal to its Constitution score before suffering any ill effects. Each additional minute spent in frigid water requires the creature to succeed on a DC 10 Constitution saving throw or gain one level of exhaustion. Creatures with resistance or immunity to cold damage automatically succeed on the saving throw, as do creatures that are naturally adapted to living in ice-cold water.
A quicksand pit covers the ground in roughly a 10-foot square area and is usually 10 feet deep. When a creature enters the area, it sinks 1d4+1 feet into the quicksand and becomes restrained. At the start of each of the creature's turns, it sinks another 1d4 feet. As long as the creature isn't completely submerged in quicksand, it can escape by using its action and succeeding on a Strength check. The DC is 10 plus the number of feet the creature has sunk into the quicksand. A creature that is completely submerged in quicksand can't breathe (see the suffocation rules).
A creature can pull another creature within its reach out of a quicksand pit by using its action and succeeding on a Strength check. The DC is 5 plus the number of feet the target creature has sunk into the quicksand.
Razorvine is a plant that grows in wild tangles and hedges. It also clings to the sides of buildings and other surfaces as ivy does. A 10-foot-high, 10-foot-wide, 5-foot-thick wall or hedge of razorvine has AC 11, 25 hit points, and immunity to bludgeoning, piercing, and psychic damage.
When a creature comes into direct contact with razorvine for the first time on a turn, the creature must succeed on a DC 10 Dexterity saving throw or take 5 (1d10) slashing damage from the razorvine's bladelike thorns.
Slippery ice is difficult terrain. When a creature moves onto slippery ice for the first time on a turn, it must succeed on a DC 10 Dexterity (Acrobatics) check or fall prone.
Thin ice has a weight tolerance of 3d10 × 10 pounds per 10-foot-square area. Whenever the total weight on an area of thin ice exceeds its tolerance, the ice in that area breaks. All creatures on broken ice fall through.
Giant spiders weave thick, sticky webs across passages and at the bottom of pits to snare prey. These web-filled areas are difficult terrain. Moreover, a creature entering a webbed area for the first time on a turn or starting its turn there must succeed on a DC 12 Dexterity saving throw or become restrained by the webs. A restrained creature can use its action to try to escape, doing so with a successful DC 12 Strength (Athletics) or Dexterity (Acrobatics) check.
Each 10-foot cube of giant webs has AC 10, 15 hit points, vulnerability to fire, and immunity to bludgeoning, piercing, and psychic damage.