The Doomguard ability, which causes physical damage to all enemies in an 8 yard radius in addition to stunning them for 2 seconds. Costs 250 mana and has a 20 second cooldown. The damage scales slightly with level, starting at 160 at level 60.
Patch changes
Patch 1.5.0 (2005-06-07): Now has a maximum of 5 targets.