This level-5 adventure is created for Dungeon Crawl Classics with a strong old-school roleplaying focus. It can be easily adapted to any RPG system. Among other elements, what makes Cathedral of the Undying stand out as a unique adventure is that PCs will not initially die when killed. A strange necrotic curse brings them back to life, but also a step closer towards becoming a mindless undead! PCs imagining this is a form of invulnerability may soon discover they have permanently joined the creatures of the night.