The Slayer Codex is the book used to record the souls of Slayer monsters that the player has captured. It is obtained from Faiza after achieving level 99 Slayer. The Codex is updated when a new creature's soul is captured in an ushabti and placed in the Chest of Souls, or when it is added to the player's personal Slayer dungeon. Completing the Codex and having unlocked the red version of the Slayer Master title from Rush of Blood unlocks the golden title.