Sleep effect

Sleep effects cause a standing sleep-like state, where the character is unable to act for the duration of the ability or until dealt damage of any kind (in contrast to Stun where damage doesn't break the effect).

Examples of abilities that cause Sleep effect:
 * Druid: Hibernate
 * Hunter: Wyvern Sting
 * Various items can also cause the Sleep effect, like Slumber Sand.

Any sleep effect, no matter the duration listed, will last a maximum of 12 seconds when used against players in PvP.

Note that a Rogue's Gouge and Sap abilities, along with a Succubus's Seduction are functionally equivalent to sleep effects, that is, they prevent the target from taking any action for a certain length of time but break on damage. However, these abilities do not actually put the target to "sleep", but are considered Incapacitate, Sap and Charm effects, respectively.

Counters

 * Ways to remove Sleep effects:
 * The PvP Trinkets
 * The Undead racial Will of the Forsaken
 * The Paladin's Divine Shield
 * Hunter's pet with the Bestial Wrath talent are immune to Incapacitate.