In some ancient civilizations the Wolf was a symbol of the underworld. In Egypt, the guardian of the dead was Anubis who was a wolf-headed god. The jackal portrayed as black was the symbol of both death and regeneration.
William is also the one who hid inside the suits and kidnapped and killed children, leading to the assumption that William Afton is The Purple Guy of FNaF 2 and 3 (he is killed at the end of the book when Charlie sets off the spring locks in his suit).
FNaF World has been released again, but this time as a free download. It's also worth noting that the maligned Five Nights At Freddy's RPG got a huge update with a 3D overworld! It's clear that its developer, Scott Cawthon, is slowly making good on his promise to please fans.