Fae Codex can viewed in the bottom right corner of the game screen, through [Mythical Beast] > [Fae] > [Fae Codex].

You can activate the Faes you have in your Fae Codex and acquire powerful Options.

Upgrade Jewel Slots with the Faes activated in the Fae Codex to increase Jewel Slot Tiers and Options, and acquire powerful Property Skills when reaching certain Jewel Tiers.

Fae Jewel Slot Upgrades can be done by using the Fae Jewels corresponding to each Slot, and Fae Jewels can be acquired from Corps BOSS Content or Events.