Grimoire♀

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.

(spoiler hidden)