The Cathedral (Sinnoh)

The Cathedral, also known as The Great Temple, is a building located north of Stark Mountain (past the in-game Sinnoh map), built atop an Aura Nexus at an unknown date, and technically on a higher sub-plane of the Material Plane. Annoski was originally sealed within the Keystone by the Aura Guardians there, and it was where he met his final defeat during the Infinity Keystone Arc. Containing architecture and artwork from what is now Kanjoh, Sinnoh, and Almia despite its superficial cathedral appearance, amongst others, and described by Annoski as a place where "only those with a strong will and a willingness to bet their own lives" can find due to magical protection obscuring it from surveillance, it remains an enigma.

In other universes

In the Yangverse, The Vow was originally consecrated at the Cathedral.

Trivia

• The Cathedral is located so far outside of civilization that large amounts of the local Pokémon have never even seen a human before, and therefore do not follow the Vow.
• Its design is based upon the Lost Cathedral from Soul Calibur III.
• The Cathedral technically isn't a true cathedral, but Tagg gave it that name out of an inability to figure out a better term to describe it. The Great Temple name given by the [Nivkh] group who visit the area monthly is actually a more accurate descriptor.