Origin

Octo started out as an oscuratype monster born from childhood fear. During a sleepover, it attacked and killed the best friends and parents of a girl that would eventually be known as Erica Slaughter. She found the courage to attack the monster, impressing Jessica Slaughter, the monster hunter who showed up to finish the job. Rather than slay the monster, she used a protection spell to trap the monster in Erica's favorite toy, a stuffed octopus. This made Octo Erica's totem that would be tamed during training and used during monster hunting.

Creation

Octo made its first appearance in Something is Killing the Children #1 by James Tynion IV and Wether Dell'Edera