These luggalds spawn in a group of three (most times) when a luggald arcanist has been dispatched originating on the spawn place nearest to the pool.
At level 59 they gave almost half a blue bubble of (real) xp, which is 3-5 times more than the normal luggalds that spawn in this room. They have quite some more hitpoints though - fight takes 1.5 to 2 times longer with same average dps.
The despawn after 5 or 10 minutes when not attacked.
My group kept the room cleared in the pool room for a while, then 3 spawned, only killed 2 of them, and dropped nothing and the 3rd one despawned, maybe spawns a named if kill all 3 before despawn, anyone have any ideas?