Fall damage
Fall damage is incurred when a creature falls several strata down. This usually happens when a creature walks off the edge of a high structure, or falls down several 
deep shafts in succession.
A creature will fall down 1 stratum automatically if they walk or are pushed into the same tile as a deep shaft or simply open air, and will continue to fall until they reach a stratum with solid ground. Creatures who are flying will not fall automatically and can choose to descend or ascend the deep shaft or open air.
Fall damage is only incurred if the creature falls more than 1 stratum downward. If the player willingly walks over a deep shaft or other drop that meets this criteria, they will be stopped and warned with the following message:[1]
It looks like an awfully long fall. Are you sure you want to jump? |
The player can choose not to jump by choosing No or Cancel. Choosing Yes will cause the player to jump and receive crushing damage based on how far they fell. Dying from this damage rewards the Free Falling achievement.
Formula
The following formula is used to determine fall damage based on distance fallen.[2]
| Fall Damage if Distance > 1 | (# Strata Fallen)d20 + (100 + # Strata Fallen × 25)
|
|---|
For example, falling down the deep shaft in 
Golgotha is 5 strata deep, meaning that anything that falls down it will take 
5d20+225230-325 (Avg: 277.5) damage.