Mangle

Mangle is a character that originated from Scott Cawthon's FNaF 2.

Role in FNaF
Mangle is an antagonist animtronic in the FNaF franchise. Her hostile appearances are in FNaF 2, FNaF 3, FNaF : UCN, FNaF VR : Help Wanted and FNaF AR : Special Delivery. She usually attacks the nightguard by vent in the games.

Role in Zajcu's series
Zajcu made Mangle the secondary antagonist in the series. Originally, Mangle appeared to be friendly before Season 4, and had a seemingly romantic love ship with Foxy. But in the 4th season, Nightmare finally revealed that Mangle was the traitor who was betraying the animatrnics the whole time and working for him. Springtrap got so angry that he tried to rip Mangle apart, only to be stopped by Nightmare. Everyone, especially Toy Chica, was shocked to realize Mangle's true identity.

Killing Foxy
Now Mangle may have had a true love bond with Foxy before, but now, under Nightmare's command, she probably didn't. Just to test Mangle's loyalty, Nightmare ordered her t kill Foxy with the Nightmare Sword. Mangle found it hard, but with Foxy begging for mercy, Mangle finally stabbed Foxy, killing him almost instantly. She might have felt a little regret, but with Nightmare giving her more power, she forgot about that. Chica witnessed Foxy's death and told the remaining animatronics about it.

Backstory
If you think Mangle went haywire or was out of her senses for becoming a villain for no reason, she told the reason in the episode The Life of a traitor. She was abused and mistreated by the resturant crew, even though the the other animatronics weren't. Then one day she found Nightmare's shadow ball. Shadow Freddy got summoned and he offered her power if she helps him. She agreed after listening to Shadow Freddy's backstory, realizing he was not any different.

Trivia
Her new name would Kangle
 * Mangle now is given an evil-looking black skin by Nightmare.
 * She hasn't appeared since a few episodes.