Stealth is one of the thief's most powerful tools in Guild Wars 2, allowing them to strike from the shadows or to run away if the fight isn't going in their favor. Stealth allows the thief to be invisible to enemy players in PvP and enemy creatures in PvE. While in stealth, the thief cannot be targeted but can be hit by AoE attacks. The thief will appear as an outline to allies while in stealth.
Guild Wars 2