The Persona Compendium is your ultimate resource for managing and understanding the Personas you acquire throughout your journey in Persona Q: Shadow of the Labyrinth. This in-game encyclopedia allows you to view all the Personas you've encountered, along with their stats, skills, and resistances. More importantly, it's the gateway to Persona Fusion, a core mechanic that allows you to combine two or more Personas to create a new, often more powerful one.
To fuse Personas, you'll need to visit Igor and Elizabeth in the Velvet Room. The process involves selecting two (or sometimes more) Personas from your Compendium or your current roster. The resulting Persona's level, stats, and inherited skills are determined by the Personas used in the fusion. Understanding elemental affinities and skill inheritance is crucial for creating optimized Personas. For instance, if you want a Persona with a specific powerful skill, you'll need to ensure at least one of the parent Personas possesses that skill.
The Compendium also tracks which Personas you've registered. Registering a Persona means it will be saved in the Compendium, allowing you to re-summon it later, even if you dismiss it from your active party. This is incredibly useful for planning fusions, as you can always re-acquire a necessary component Persona from the Compendium, provided you have enough Yen. The cost to re-summon a Persona is based on its level and rarity. Mastering Persona Fusion is key to overcoming the toughest challenges in the Labyrinths, allowing you to tailor your party's strengths to exploit enemy weaknesses and overcome formidable foes.