Overview

• The Key of Apostate is identified as one of three Slab Keys that unlock a sealed door in the Slab for endgame progression.
• PCGamesN reports the key sits in the Putrified Ducts and is reachable from Bilewater or via Memorium, with the Double Jump (Faydown Cloak) needed.
• Destructoid outlines a route from the Bilewater bench requiring Wall Climb, Dash, and Double Jump, noting the absence of objective markers.
• Both guides describe a demanding path filled with enemies, vertical sections, and precise platforming before reaching the key.
• Nerd’s Chalk additionally claims access opens after defeating Groal the Great and suggests possible rewards like a Needle upgrade, which remain uncorroborated by other outlets.