Warhammer 30k and the Great Tomb of Nazarick

A church in the Slane Theocracy, on the verge of annihilation by the Great Tomb of Nazarick, discovers an unclosable portal connected to the world of Warhammer 30K. Thus, Warhammer meets the Great Tomb. Ainz Ooal Gown: "Oh no, I've become a native!" PS: This is an expanded adaptation of my answer to "What would happen if the human empire from Warhammer 40k's Great Crusade era discovered the isekai world from OVERLORD?" The original answer is complete, but many plot points in this fanfic have been revised and differ from the original—hope you all enjoy!