Eightfold is the name of the spirit possessing Isabel's book. She is a relatively weak spirit, readily accepting her role as Isabel's tool.
Personality
Eightfold is chipper and somewhat eccentric, as seen when making a quip about "stretching her legs...all 8 of them" before laughing. She's also prone to messing with people, as she flies over to Max and teases him about the possibility of controlling his own poop with her power if she possessed him and made him her medium while Max becomes visibly uncomfortable. Eightfold genuinely cares for Isabel, complimenting her skills in tool use, her ability to bond with spirits to the point that they can somewhat sense her emotional state, and her good heart while also advising her about lessons she unwittingly picked up from her grandfather on seeing spirits as less than people.
Biography
At one point, Eightfold's book was in the possession of Francisco Guerra, who had given it to his granddaughter, Isabel, after an accident in order to help her defend herself. Eightfold then began regarding Isabel as a friend, and vice versa. Isabel has been using her book as her main choice of weapon ever since.
Paranatural
Eightfold is summoned during Study Hall by Isabel in order to show her off to Max. Eightfold greets him in her own way while devouring a book Isabel had gifted her. As she begins creeping Max out, Isabel punishes her by swatting her. Eightfold regards the actions and words as similar to familiar person, before she agrees to go back into her book.
During the fight in the Ghost Train, Eightfold's book is kicked off the Ghost Train by a Vile Spirit. Eightfold immediately pulls Isabel into a trance. During this time, she asks Isabel to recount the time they met, afterwards pointing out that important details were not involved, even her. Eightfold tells her that although she thinks Isabel is a kind person and selfless by instinct, she unconsciously treats Eightfold as less of a person, and more of an object; a lecture she hopes Isabel will understand later on. She then reveals she had been stalling Isabel to prevent her from going after the tool and leaving Max open to attack, saying his protection should be her top priority. Eightfold proceeds to to say goodbye prematurely, and blubbers out for Isabel to create her own story and to treat her new partner better before she senses that Isabel will miss her. After proclaiming she felt the same way, the trance ends and the book is presumably buried under the earth outside Mayview.
Relationships
Isabel Guerra
She is shown to be quite friendly with her spectral, claiming she is "Naturally good", even sacrificing herself so Isabel would save Max instead of her.
Abilities
Eightfold is a weaker spirit meaning that she can regenerate energy fairly quickly if defeated, only needing a few days to get back to full strength. Thanks to this she can leave her tool and interact with other members of the Activity Club when needed, simply cutting herself apart when she needs to possess the book again. As a smaller spirit she can also fit into small spaces. Since she can interact with physical objects by eating books to gain the knowledge inside them, she is classified as a poltergeist.
Papercraft
Eightfold's primary ability is to eat paper, absorbing the words printed on them, and making constructs out of the paper waste left behind. She can modify her body in many ways through this such as adding wings, bladed scorpion tails, and can even fashion elaborate clothes. Constructs like the winged horses and storms of pages that Isabel can make while Eightfold is inside the book tool are material meaning that non-spectrals can see and interact with them.
A side-effect of Eightfold absorbing the words off the pages she eats is that she is very knowledgeable with essentially a functionally photographic memory for any subject she's eaten before.