Springtrap

Springtrap is the main antagonist in Five Nights at Freddy’s 3. Springtrap is William Afton's reanimated corpse that was crushed in the spring-lock suit.

Springtrap was made when William Afton was killed inside of the Spring Bonnie spring-lock suit after fleeing the spirits of the children he murdered in the past, thinking they would not see him hiding in the spring-lock suit not knowing of his death. He was found sitting in the safe room at Freddy Fazbear's pizza and survived the burning of Fazbears Fright and later became Scraptrap in FFPS as a salvage animatronic.

History
As the games have told us, Springtrap is the rotting corpse of a murderer William afton or was known as Purple guy. After he dismantled the animatronics, the free roaming spirits of the children of that past murders haunted William and as they did William entered the old springlocksuit to hide from them, as he mentioned in The Silver Eyes novel that he is  one of them . William laughs at the dead children before the spring-locks become unstable, killing William in his own blood. Many years later the manager of Fazbear's Fright found the suit as it was left to rot, as it was the only featured animatronic in the attraction. After Fazbear's Fright burned down he was not seen in further games until FNaF6 or FFPS came out as he appeared as Sraptrap. He appeared again in FNaF Help Wanted in the FNaF 3 gamemode.