Each child is assigned a monster from their birth until they're at least fifteen years old. Some children gets re-assigned. Some children keeps their monsters their whole life. Some children do both. Tags from AO3: Alternate Universe, Monsters, Horcruxes, Hadrian raises himself but also not, Hufflepuff Harry, Unhealthy Relationships, Obsessive Behaviour, Unhealthy Coping Mechanisms, Immortality Happy HalloweenAll Rights Reserved