A council-style fight with Karathress and three Fathom-Guards. Each guard killed grants Karathress a new ability.
Four tanks needed, one per enemy. Kill order: Tidalvess (Shaman) first — kill Spitfire Totems immediately. Then Sharkkis (Hunter) — control his pet. Then Caribdis (Siren) — tank her far away to prevent her healing allies. Finally Karathress himself. Each dead guard gives Karathress a new ability, so the fight gets progressively harder. Casters can split to DPS Caribdis while melee handle the kill order. Interrupt Caribdis's Healing Wave.