Environment
Falling
When you fall from a great height you instantly descend up to 100 units per turn. A fall from a great height is one of the most common hazards facing an adventurer. At the end of a fall (more than 2 units tall), a creature takes 1d4 bludgeoning damage for every 2 units it falls to a maximum of 20d4. The creature lands prone, unless it avoids taking damage from the fall.
Suffocating
A creature can hold its breath for a number of turns equal to 1 + twice your endurance (minimum of 2)
When a creature runs out of breath or is choking, it can survive for a number of rounds equal to its Endurance (minimum of 1 round). At the start of its next turn, it drops to 0 hit points and is dying, and it can't regain hit points or be stabilized until it can breathe again.
Difficult terrain
you spend 2 units of movement for every 1 unit while in difficult terrain.
Senses
Tremorsense
A monster with tremorsense can detect and pinpoint the origin of vibrations within a specific radius, provided that the monster and the source of the vibrations are in contact with the same ground or substance. It can't be used to detect flying or incorporeal creatures.
Darkvision
A monster with darkvision can see in the dark within a specific radius.
Cover
Total Cover
While on total cover, you cannot be targeted by attacks.
High Cover
While on High cover, you add a +4 to your dodge and reflex saving throws.
Low Cover
While on Low cover, you add a +2 to your dodge and reflex saving throws.