Standing on the sand will cause mobs to spawn. The boss spawns a cloud which moves around the room and will gib people. Periodically, he will spawn adds and despawn the cloud. The presence of the adds increases the boss's damage.
Tank the boss in the corner of the room that is currently opposite of the cloud of nastiness. When moving the boss, jump across the sand as much as possible to avoid spawning adds. DPS down adds when present.