The enormous starship of Kukulkan, an ancient visitor once worshipped on Earth as a god, which trapped the Enterprise and took the form of a winged serpent.
Kukulkan's ship appears in the animated episode How Sharper Than a Serpent's Tooth. The Enterprise meets it while tracing a probe that scanned Earth. The vessel holds the Enterprise in a globe of force and then changes shape into a huge feathered serpent, which Ensign Walking Bear recognises as the Mayan and Aztec god Kukulkan.
Kirk, McCoy, Scott and Walking Bear are taken aboard. Inside they find a model city mixing the styles of several ancient Earth cultures, a puzzle they must solve to summon their host, and a collection of animals kept content in illusory habitats.
Kukulkan intends to resume guiding humanity. Kirk frees a Capellan power-cat to distract him and argues that humans have outgrown the need for such a guardian.