Monsters are the primary enemies in the St. Abraham series. They are warped physical manifestations of pieces of each protagonist's psyche. They appear in our dimension because of the rituals performed by The Hallowed.
Each monster symbolizes some aspect of the main protagonist.
All of the monsters represent various mental disorders or the status of Jay's psyche.
All of the monsters represent tragic or traumatic events in Owen's life.
All of the monsters represent Zoe's feelings about her school or her insecurities about her appearance.