Created by Nine the Phantom during the Dark War, grimoire are used to control Ars Magus by using the seithr around the air. They are controlled by the NOL, who create them, manage them, and regulate them, leading to what some call a monopoly and leading to their nickname of the "Library".  Not all grimoire were created by the NOL or Nine, as some existed up to 50 years before the Dark War even began.
Grimoire do not necessarily take the shape of a book, and can be found in the shapes of various different objects, such as a mirror or scales. More advanced versions of grimoire do exist, such as the Ars Armegis and Nox Nyctores, and depending on the degree on which a grimoire is smelted, they can be assigned different ranks and power. A grimoire and a person can fuse to become one and this is known as a Remix Heart. They are exceptionally rare and only one has been known to exist. At some point, various grimoire went missing in the 15th Hierarchical City of Torifune and various ones were rediscovered by Team Remix Heart.
In the XBlaze possibility, a Grimoire is more an ability, not an object. Anyone with this ability is capable of using the XBlaze technique, an ability that stores seithr for later use. Three exist in the XBlaze possibility, one of which was replicated and exists in the BlazBlue possibility.
List of Grimoire
- Azure Grimoire - possessed by Ragna the Bloodedge; said to be both the strongest and weakest Grimoire
- Hazama - is a Blue Grimoire
- Kazuma Kval - is a Blue Grimoire
- No-Name Grimoire - possessed by Mai Natsume; they are a Remix Heart
- Burning Red Grimoire - unknown location; last seen in the possession of Hazama
- Aedsqui Grimoire
- Aequivalentis Grimoire
- Ammit Cryas
- Conversion Grimoire
- Evolution Grimoire
- Guardian - also known as the Will Finding Grimoire
- Hypnagogia Grimoire
- Intermediary Grimoire - no longer exists 
- Regulation Grimoire
- Anti-Demon Beast Grimoire
XBlaze possibility Grimoire
BlazBlue: Central Fiction Library Entry
Magical items that can utilize Seithr. They were created by one of the Six Heroes during the war against the Black Beast. Grimoires have different ranks, and their power depends on the degree to which they were smelted. Basically all magic weapons are equipped with Grimoires.
- BlazBlue: Chrono Phantasma, Teach Me More, Miss Litchi! Tip 1: Calamity Trigger Review
- BlazBlue: Remix Heart, Chapter 25
- BlazBlue: Central Fiction, Library Mode, Item #004