Like any good villain, William derives his reward from the instruments of death he has constructed to carry out his murders. Sneaking into the pizzeria to collect his victims’ supernatural residue left behind in the animatronics, William is ambushed by their ghosts that haunt the robot suits. William is stuffed into a spare Spring Bonnie animatronic and crushed to death similar to the murders he committed. However, much like those he murdered, William finds his spirit haunting the animatronic he is killed in, taking on the nickname Springtrap.
Equally deadly post-mortem, William’s spirit continues to haunt other animatronics in later games after Springtrap’s destruction. The franchise needs a human antagonist, not just a largely silent animatronic, and William fulfills that while adding to the lore. William’s eventual death at the hands of his murderous creations seems both cathartic and poetic, and fitting for his crimes. And if there’s anything that could set up a potential sequel, William’s monstrous revival as Springtrap lends itself perfectly to that possibility.