Equipping a Grimoire in allows you to cast specific magic from its texts, but Unique versions of these spellbooks contain multiple pieces of arcana you can wield.
Once you get a rare Unique Grimoire, you can access the signature spells of whoever used those books before. These are always prepared collections of four powerful, distinct magical abilities that can completely change how you play the game.
Similar to Unique weapons and armor in , Unique Grimoires are scarce items of high quality that are usually attached to side quests or thorough exploration. Each Unique Grimoire comes with four spells based on the knowledge of each tome's previous owner.
While you can learn the spells in these Grimoires separately, having them in addition to the magic you know could help complete a strong spellcaster character build.
There are six Unique Grimoires scattered around the world, with some only being accessible once you progress enough through the main story.