グリモワール

A mysterious being capable of controlling worms, she infiltrates stories so that the worms under her command can devour the pages which constitute the story for her own ends. Her ability to freely enter and leave the story world without the use of the Great Library perplexes Historia and the others for much of the game. In addition, she can sense weaknesses in the main characters of a story and directly corrupt them with worms which latch to their subconscious desires and manifest them.

 The Register of the story written by Historia, she is originally named Iris and is kept alive by Historia through fragments of other stories regularly regaled to her as she struggles to mature. She is unable to speak, and when her existence becomes too fragile to materialise in front of Historia she is thought lost by Historia and Shiori to the worms.

The white worm (later Mushiko) consumes her, but her deepest desire to show Historia a story she would be proud of spare her from oblivion and transforms her into a worm-Register hybrid who must continually devour the pages of other stories to maintain the existence of her own broken world. She later adopts the name "Grimoire" and only reveals her true identity after kidnapping Tale.

After Tale succeeds in creating a stable story world through her diary, Grimoire is exorcised from her worm aspect but her neglect and abuse of Mushiko are a factor behind Mushiko's eventual berserk outburst. Grimoire eventually pacifies Mushiko in the battle at the Great Library, and resolves to make amends for her past transgressions by working as a Librarian under Historia's supervision. Extremely competent and organised, she soon supplants Shiori's role in the Great Library and works hard to prove herself in the eyes of Historia to whom she is absolutely devoted to. /