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).
~ Big Brother forcing his brother's head into Fredbear. Big Brother (or Foxy Mask) is a major character and a true main antagonist in the Five Nights at Freddy's series, first appearing in Five Nights at Freddy's 4 as the game's tertiary antagonist, but the main antagonist in the mini games. He is the protagonist's abusive older brother, and is the one who caused the child's accident.