Achievement : Open the Thrice-Locked Cage during the Thok the Bloodthirsty encounter in Siege of Orgrimmar on Flexible, Normal, or Heroic difficulty, and then allow its inhabitant to feast upon Thok's corpse once you have defeated the encounter.
This one is kinda nasty, I'd imagine certainly not doable on normal. Have to have 2 jailers spawn each phase which means the P2's need to be extended and the jailers need to die quickly. First key is used to free the normal npc, the 2nd to unlock one of the 3 locks on the snails cell.