Grimoire

Grimoires  refers to devices, usually in the form of books, containing knowledge about magic. In Trinity Seven, information about the Thema of a magician is recorded in grimoires to help them in their research.

A grimoire doesn't have to be in the shape of a book, for example, Mira's grimoire, Book of the Mirrored Lands, takes the form of a crystal ball, while the Headmaster's grimoire, Solomon's Gate, is, as its name indicates, a huge gate following him everywhere, and cannot be seen unless you possess a certain amount of magic.

Currently, only Hijiri, and by extension Arata, have been shown to be powerful enough to have contracts with more than one of the legendary grimoires.

According to the headmaster, whenever one is fighting a magus of a higher level, equipping one's grimoire is indispensable.

Known grimoires

 * Astil Manuscript/Sora (Owner: Hijiri (former), Arata (current)): A legendary grimoire, described by Lilith as containing information about another world. In terms of pure magical power, Sora can act independently and is much more powerful than Ilias Fragment, however, much less crafty. It normally looks like a small book bound in chains but can assume several other forms, including a female human.
 * Astil Manuscript/Radix (Owner: True Demon King): The real Astil Manuscript. She can be thought as Sora's mother, and it’s also how Sora and Arata refer to her (Sora’s mother). Like Sora is grimoire for Arata the Demon King candidate, she is the grimoire of the True Demon King and is very loyal to him.
 * Ilias Fragment/Ilya (Owner: Hijiri (former), Arata (current)): A legendary grimoire, sometimes she would take on Hijiri's memories and appearance to act as a substitute when Hijiri was out of the house on magus duty. Self-described as a " Support-type grimoire". 
 * Hermes Apocrypha (Owner: Lilith). Written and previously owned by Hohenheim, the ancestor of Alchemy. When reacting with Arata’s demon king factor, she can take human form named Lilim. She refers to Arata and Lilith as her Papa and Mama.
 * Yggdrasil Laguna (Owner: Arin): This grimoire is mostly seen as a ring on Arin's finger.
 * The  Book of the Mirrored Lands  (Owner: Mira)
 * Solomon's Gate (Owner: Headmaster): As said before, it is invisible to all unless they  possess a certain amount of magic. According to the Headmaster, even the stronger magi lose their minds after staring at it for too long.
 * Aleister's Score (Owner: Yui)
 * Archytas Replicator (Owner: Selina)