Springtrap

Springtrap, later known as William Afton, is the main antagonist of Five Nights at Freddy's 3 and a returning character for the Ultimate Custom Night.

Appearance
Springtrap is a greenish-yellow springlock suit holding the corpse of William Afton. He used to be yellow but decayed over the years. He is a dark green in color, with yellow/green eyes resembling those of a human being. Springtrap's body is heavily tattered, especially his torso and arms that expose his human flesh. He also appears to wear a black button on his torso, possibly hinting at his past occupation at Fredbear's Family Diner.

He has two sets of teeth, one on the bottom and one on the top. His ears are broken, mainly the right one, which is missing the rest of it. His eyes are larger than the regular animatronics'.

Ultimate Custom Night
He climbs around in the vent system, making his way toward the vent opening embedded in the wall in front of you. Track him by watching the vent monitor. He moves silently, so don't bother listening for him, but when he is poised to attack you will see his face looking back at you from the vent. Close the vent door on him to send him away.

=Gameplay= He climbs though the front vents to get into your office and jumpscare you. You can see him in the Vent Systems monitor and he always pass by the right vent to go in the "crossing". He can't be stopped by the vent snare but you can see him peeking at you when he's about to attack you and close the front vent door to block him.

Trivia

 * Springtrap was programmed together with Molten Freddy and Ennard at 40%.
 * It's clearly unknown how Springtrap changed his appearance during the events of Pizzeria Simulator, although it's possible he salvaged some animatronic parts to repair himself after being damaged in the burning of Fazbear's Fright.
 * Springtrap is one of the 5 animatronics that climbs into the central vent, the others being Withered Chica, Mangle, Ennard, and Molten Freddy.
 * Springtrap, along with (possibly) Golden Freddy, are the only animatronics that presumably originate from Fredbear's Family Diner.
 * Springtrap's groans are actually edited alpaca noises.