Icy Devourer  

Spawn time on the icy ooze is about 20 minutes.

We started out clearing the room and then clearing the tank, but after two rounds of in and out of the water, we decided to just hop in and set up camp in the water.

Once in the water, we were unsure what, exactly, would get pulled down into the tank with us. Upon experimentation, it seems that as long as you stay close to the bottom, you only get a random nightmare guardian and serpent.

We had to kill the tank a total of five times before the Icy Devourer spawned (that includes the two we did clearing the room first). Nothing special about the attack of the mob, but definately not a mob I'd want to take on with adds. We were lucky in the sense that we had spaced out the kills nicely, and therefore had spaced out the pops nicely as well.

He dropped the sword - and as we are only working on the Hunter trophies at this time, we didn't hang around to see if he respawned after we killed him.