The entire story of Five Nights at Freddy's involves numerous creepy animatronics, but it ultimately revolves around a single character. William Afton is personally responsible for almost every horrific event in the series, as he's the co-founder of Fazbear Entertainment and the one who originally built the iconic animatronics. In the Five Nights at Freddy's lore, he's also the murderer of the children that now possess those various suits, which attack the player throughout the games. This makes William Afton, AKA the Purple Guy, easily the most important character in the series, not to mention the most resilient.
Source：https://www.cbr.com/fnaf-william-afton-purple-guy/
