First appears in: The Twin Fury
Grace Cathedral is a breathtaking, meticulously rebuilt church located in the floating city of New San Francisco. Constructed at the behest of the Cothellon leadership, its existence is a mystery to many: "They’d insisted on having the wedding at Grace Cathedral, probably because Lorelei had been the one to insist that Grace Cathedral should exist to begin with. They hadn’t needed to rebuild San Francisco from the ground, keeping everything the same, but for some reason Lorelei had wanted it to be that way". The interior is a marvel of old-world architecture, featuring "white archways atop wooden pews—real wood!—leading up to the vaulted ceiling high above. The sanctuary ended with a huge pipe organ, reproduced in every exacting detail from the original organ in the ruins below".
The cathedral serves as the venue for Trey and Lora’s wedding, a union secretly orchestrated by Quynn in his twisted attempt to breed a new Prime Mage. Walking into the ceremony, Trey feels completely alienated by the opulence, noting that despite the beauty, he felt "apart from it, adrift in a floating world that did not know his name."