This quest used to be the access quest for the Sanctum of Fear, but it's completion is no longer required to enter the instance.
Later in the quest, you will need four clay golem hearts, which drop from the corpses of clay golems wandering the zone. You may loot them prior to being on the quest.
Kill the Acidic Mass at ( 0, 44, -214 ) Copy/waypoint 0, 44, -214. It is the last spawn of a ring event started at the pool down the back stairs of the central pyramid on the upper terrace.