WOW Insider

After blowing through the Wyrms, you'll get to the second boss, Vexallus. The immediate comparison here is to the Curator from Karazhan: he periodically spawns an add that needs to be DPSed down lest it chain-lightning everyone to death. The adds don't have much health; however, the person who kills them gets a de/buff, which ticks for 300 damage per second but increases the damage they do by 50%. It might be best for the DPS classes to rotate who kills the adds, so that nobody's dropping in health too fast. When Vexallus gets to 10% health, he Overloads and starts AoEing the heck out of your party. At this point you need to just burn him down as fast as possible; save your cooldowns for this part of the fight.

screenshot via Wowhead

28/03/08