Slayer Codex - The RuneScape Wiki

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. Removing a monster from the slayer dungeon will not remove the soul from the Codex.

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Slayer Codex List, organized after area, and an order in which you can do them all : r/runescape

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Slayer Codex List, organized after area, and an order in which you can do them all : r/runescape