Monsters (and you!) can be put to sleep by a number of different means:
- The "sleep" brand (unique to needles)
- Ensorcelled Hibernation usable by the player, and a few monsters: The Enchantress, player ghosts, and some pandemonium lords.
- The monster-only "sleep" spell, usable by Aizul.
Monsters are usually asleep at the time that they are generated (or "dormant", if incapable of sleep), and tend to fall asleep again if enough time has passed since they last encountered the player.
The player character will always wake if he/she takes any amount of damage.