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).
Purple Guy. The Purple guy is a suspected killer and has been considered one of the most intriguing characters within the Five Nights At Freddy's plot, for having little information available throughout the entirety of the games, much similar to how the Bite of '87 was before the fourth game in the series.