The jewel in the Crystarium's crown is the Rubicus, located right near the entrance. It's an incredible anthology of records, dossiers, and all sorts of advice. If you ever find yourself at a loss, I'd first try consulting the Rubicus.
The Rubicus (朱の目録, Aka no Mokuroku?), also known as the Crimson Codex, is the in-game encyclopedia of Final Fantasy Type-0, containing data on lore, characters, and gameplay explanations. It can be accessed in the Crystarium in Akademeia or from the History option on the title screen. It constantly updates as the player progresses through the game.
The Rubicus is divided into six sections:
- Annals of Orience
- Chronicles the history of Orience, including documentation of events prior and during the main story. Also doubles as an Event Viewer for cutscenes.
- Historical Personae
- Contains profiles of the game's characters, including battle statistics for Class Zero.
- Eidolon Arcana
- Contains profiles of the game's Eidolons, including battle statistics.
- Enemy Compendium
- Contains profiles of the game's enemies, including battle statistics.
- Record of Service
- Contains archives of the game's Tasks as they are completed.
- Code of Akademeia
- Contains archives of the gameplay explanations.
- The background of the Rubicus is thirteen numbered clockwork wheels. The game has some allusions to the number thirteen due to originally being called Final Fantasy Agito XIII. This background also appears on the ceiling of a concept art for an unused location: Arecia's laboratory.
- The cover of the Rubicus has a depiction of Etro's gate on it. This is one of many references to it in Final Fantasy Type-0.