Cetus was an Asuran, serving under Talus during the Asuran assault on Atlantis. When Major General Jack O'Neill and Richard Woolsey were captured, Cetus probed Woolsey's mind for whatever information he held. Once the Asurans had repaired the damage to Atlantis, Cetus activated the shield in preparation for Atlantis' journey to Asuras. However, Lt. Colonel John Sheppard's team had rigged the shield emitters with Replicator disruptor crystals that resulted in a disruption wave spreading through the city, destroy Cetus and the other Asurans. (SGA: "The Return, Part 1", "The Return, Part 2")
- It's possible that, like Oberoth, Cetus could be replicated again, though he would have died in the destruction of Asuras.