Leviathan (Kingdom Hearts III)

The Leviathan is a monstrous Atlantean autonomous vehicle that guards the undersea entrance to Atlantis. The Leviathan resembles a lobster, much like the other Atlantean vehicles resemble sea creatures. It (or perhaps another of it's kind) can be seen flying in the opening prologue.

In the first visit to Atlantis, the Leviathan attacks the crew of the Ulysses and the Keybearer gang to try and prevent them from entering the lost empire. Sora manages to weaken the creature and send it away for a while, allowing his friends to escape the creature. Later on, while Rourke tries to escape Atlantis with the Heart of Atlantis/Kida fusion in tow, Xemnas warns him of Maleficent's arrival to the city and alerts him to hurry up in his mission. Sure enough, Maleficent and Dr. Facilier arrive to steal the crystal away from both Rourke and our heroes. To capture the crystal for the Villains Vale alliance, Dr. Facilier uses the powers of darkness to corrupt the Leviathan, turning it into a Heartless, and then ordering the monster to obtain the crystal and destroy Sora at all costs. Sora fights off against the Leviathan by summoning both Elliot the Dragon and Genie to counter the Leviathan's devastating thunder and claw attacks. Eventually, Sora is able to destroy the Leviathan using the Keyblade, sending its heart to Kingdom Hearts. But he must now confront an angry Rourke, who has now turned into a Rage Glower...