The Episode 33: Atlantis Add-on for DC Universe Online has 3 achievements.
During the Atlantis: Silent School (Normal) Alert, in the first boss fight, all Thorn Magi must be hit at least once by the Thorn Golem's Timber attack.
During the Atlantis: The Throne (Elite) Raid, defeat Sea Beast without anyone in the group being picked up and chewed on by the Sea Beast during one attempt at the fight.
During the Atlantis: Crown of Thorns (Elite) Raid, prevent King Shark from using his Feeding Frenzy on your group mates throughout the encounter.