The Leviathan

Although the Heart of Atlantis was a gift from the High Council, some parts of the crystal CAN be corrupted by the Friends into objects of darkness and despair. One of these crystal segments was the Leviathan, the guardian of Atlantis, now corrupted into an all-powerful agent that collects the souls of anyone who dares try to find Atlantis. However, its attack on the Ulysses wasn't intended by the Friends, as it killed most of the crew and Rourke's own elite squadron of gas-mask mercenaries. The Leviathan still remains in the sea, under orders from Ursula to conquer Atlantica by any means necessary.