Sleep is an effect players or monsters may encounter in NetHack. While asleep, you are immobilized for a number of turns. Sleep resistance prevents this from happening. As of Nethack 3.6: You hear sounds are prefaced with "You dream that".
Ways to fall asleep
- Drink or be hit by a potion of sleeping
- Be zapped by a wand of sleep
- Be hit by a sleep spell
- Put on an amulet of restful sleep
- Step on a sleeping gas trap
- Be attacked by a homunculus or hit by the sleeping breath of the orange dragon, Nazgul, or the Chromatic Dragon. Magic cancellation protects against the sleep-inducing homunculus bite.
Free action prevents sleep from potions of sleeping only.
Some of the above events can also affect monsters, and some monsters (notably nymphs) are generated sleeping. Monsters affected by sleep attacks will sleep for a number of turns and then wake up. Those generated asleep will only wake up when you approach (if you do not have stealth) or attack them.