Sin expands on the world described in Spire: The City Must Fall and delves deeper into three different facets of life within the crumbling walls: Crime, Religion and Order. Extensive sections on each provide setting info, plot hooks, optional rules and new enemies to fight. Learn about the portable shrines to Rob, the God of Mugging and his unwilling benefactors; discover the latest pyrrhic trends in high elf military fashion; attend the raucous funeral-parties of the Crimson Vigil; take a look at the inner workings of the Hive, Spire's premier prison; and form your own gang of Knights who are definitely ordained by the goddess and not just hustling passersby for cash. Two new classes -- the divine con artist Gutter Cleric and the necromantic bureaucrat Mortician Executioner -- allow players to hustle gods for their metaphysical loose change or declare someone living legally dead then correct the inaccuracy at the point of a sword.