The Cathedral Ship is a massive type of Gnosis roughly 16,000 kilometers in diameter. For comparison, Lost Jerusalem is about 8,000 miles or 13,000 km in diameter (because Lost Jerusalem is not a perfect sphere), meaning the Cathedral Ship is slightly bigger than Lost Jerusalem. It received its name from the many shrine-like objects on its exterior and the countless Gnosis that accompany it.
In Episode I, the Elsa became lost inside a Cathedral Ship that was the transformed planet Ariadne, which vanished during a Zohar Link Experiment with a Zohar Emulator. Remnants of the planet are also found inside the Cathedral Ship when exploring it. Gnosis are attracted to the Zohar as well as to its emulators, so, when the Woglinde attempted to leave with the Zohar Emulator, the Cathedral Ship sent legions of Gnosis to collect it. The Zohar Emulator remained inside of the Cathedral Ship until Shion Uzuki and friends were drawn into its core. Commander Andrew Cherenkov, sent to retrieve the Emulator for Margulis, was turned into a Gnosis right in front of the protagonists, just before its disappearance. The Zohar Emulator then fell into the hands of the Kukai Foundation.
- The Cathedral Ship has a completely random sign of fish with "Why?" on it.