World of Sighs
Exhaustion: every time you drop to 0hp, you gain a level of exhaustion.
Hit Dice: call them Recoveries.
Short Rests: each short rest, you can spend a recovery to:
- roll HD+CON mod and recover that number of HP (to a cap of 2/3 HP maximum)
- remove a level of exhaustion
- regain a 1/rest ability