Grimoire

Grimoires  (魔道書), refers to the devices of sorcery, 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.

There are some grimoires that doesn't have to be in the shape of a book: for example, Mira's grimoire, the 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)): The legendary sentient 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 she can assume her human form.
 * 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 how Sora is the 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)): The legendary sentient 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. Unlike Sora, she referred as a " Support-type grimoire". 
 * Hermes Apocrypha/Lilim (Owner: Lilith (as her mother), Arata (as her father)): The sentient grimoire and magic-born daughter of Arata and Lilith. She was created and once owned by Hohenheim, the ancestor of Alchemy. When reacting with Arata’s demon king factor, she can take human form.
 * 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 mages lose their minds after staring at it for too long.
 * Aleister's Score (Owner: Yui)
 * Archytas Replicator (Owner: Selina)