It’s a empty suit being controlled by the most vengeful spirit of the missing children. It even has a little girl’s voice. It hates William and wants to torture him. Killing him would be too nice of her. The suit is actually all in your mind and is a hallucination. It uses hallucinations as a distraction to slowly kill people. It’s friendly to the other Animatronics/missing children but is very aggressive to everyone else. She doesn’t like speaking much either.