One day, in the alleyways, a strange entity known as the Outsider appeared out of the fog. The Outsider had come to grant the boy supernatural abilities, through branding the child with his mark. Once the boy had obtained these abilities, his fear subsided, and he was confident enough to confront his tormentors.
With his newfound powers, the boy decided to test them on the children who had beaten him throughout the years, and as he approached his bullies, the boy called forth a large swarm of rats to devour them. However, this unintentionally led to him being bitten by one of the rats, and the child developed a case of rat plague, leading to his death.
Similar to Corvo Attano, the unknown child possessed the ability to summon a devouring swarm of rats.