The Castle of Lions was built over 10,000 years ago, with Coran's family having taken part in the construction. After the betrayal of Zarkon, the Black Lion of Voltron was sealed in its hangar within the castle, which was then sent to the planet Arus with Princess Allura, Coran, and-unbeknownst to anyone-the Space Mice aboard in stasis. The castle remained hidden for 10,000 years, during which the Arusians came to believe it was the home of a "Lion Goddess." Finally it was found by the Blue Lion, which brought a group of five humans to the castle who awakened the sleeping Alteans. Allura and Coran would then set to repairing the castle while the Paladins set out to recover the scattered three Lions in order to unlock the Black Lion.
The castle was soon attacked by Commander Sendak's ship, which was soon able to take down the particle barrier due to advances in Galra weapons technology. Fortunately, the castle was saved by the formation of Voltron, which allowed Allura and Coran to start work on repairs.
The Castle of Lions has two modes: it can land on the surface of a planet or other astronomical body and assume castle form, or it can function as a battle ship. It comes equipped with artificial gravity, which allows the crew to travel normally while in space regardless of the ships orientation.