When a wizard casts a sleep spell, he causes a comatose slumber to come upon one or more creatures (other than undead and certain other creatures specifically excluded from the spell's effects).
All creatures to be affected by the sleep spell must be within 30 feet of each other. The number of creatures that can be affected is a function of Hit Dice or levels.
The spell affects 2d4 Hit Dice of monsters. Monsters with 4+3 Hit Dice (4 Hit Dice plus 3 hit points) or more are unaffected. The center of the area of effect is determined by the spellcaster. The creatures with the least Hit Dice are affected first, and partial effects are ignored.
For example, a wizard casts sleep at three kobolds, two gnolls, and an ogre. The roll (2d4) result is 4. All the kobolds and one gnoll are affected (1/2 + 1/2 + 1/2 + 2 = 3 1/2 Hit Dice).
Note that the remainder is not enough to affect the last gnoll or the ogre.
Slapping or wounding awakens affected creatures but normal noise does not. Awakening requires one entire round. Magically sleeping opponents can be attacked with substantial bonuses (see Combat, page 90).
The material component for this spell is a pinch of fine sand, rose petals, or a live cricket.