Zuramat is a large void lord that is caged on the west side of the Violet Hold. Throughout the fight he will summon Void Sentries that will hit the party with a Shadowbolt Volley every few seconds - the only way to kill them is to get the Void Shifted debuff, which is obtained after getting hit by the boss with his Void Shift attack. This gives you a 15 second window to kill the void adds. Another strategy is to burn down the boss as fast as possible and ignore the adds - which will depend on your healer's effectiveness, as the damage being inflicted to the whole party can become massive towards the end of the fight.