Ert

Ert is a completely charred version of Tre, and his name is Tre backwards. Ert still has his right arm, unlike Tre. The sun marking on his chest is glowing orange and his eyes and mouth are red, but everything else is black. He carries around Tre's old hand pistol, but he never uses it. (Unless he's in a grudge match with Tre, like he usually is)

History
(See Ayden Hoffman for human life) After the fire, the company found Ert and dismissed it as a burnt Tre suit. They took him to the new location and put it in the safe room. But sometimes, Ert will awaken at night. He never goes to attack the guard, but he does have a hatred for all the animatronics, especially Tre. They know what he did. But Ert also has a rivalry with Shadow Special.

Five Nights with Ayden
In Five Nights with Ayden, Ert is a threat who constantly tries to go after Richard Webster. Betty constantly remarks that a red-eyed individual was behind the murders, and Ert confirms that it was him in the Night 5 call and in the 5/20 cutscene.

In Five Nights with Ayden 2, a new, more mangled form of Ert known as Rouge Ert tracks down Sam Benedict.

In Five Nights with Ayden 3 (Past), Ert is absent. Instead, Ayden Hoffman gives phone calls to the test subject.

In Five Nights with Ayden 3 (Present), Ert again returns to attempt and kill Richard Webster.