Endo-Evil

Endo-Evil Is a reoccurring Character in the series. He appeared in the very first game and several games after.

Background
Endo-Evil is seemingly a failed creation of an endoskeleton, as the model has a unfriendly look to it, as it possesses horns, spikes and missing eyes. The model was scrapped due to this, but kept in storage in case it could be used for something else. But he was never fully deactivated.

Role In Story
Endo-Evil appearing as one of the first Characters in the series, it never was used, thus it was put away, but it was thought to move in the night, so a guard was hired to watch a small location where it was, showing it indeed would activate during night.

Office Duty
Endo-Evil is sat to the left of the player, and periodically is heard breathing, and when it is heard, you must turn and wait for about 2 seconds prior to the breathing, then flash it to cause it to deactivate.

FredBear's Ultimate Custom Night
Endo-Evil periodically arrives in the office in front of you, but only when you aren't looking in front of you. When he does appear, you must look away from him or he will jumpscare you.

Endo-Skeleton Ultimate Custom Night
Endo-Evil is apparently chained in another room, and the player must periodically repair the chains on the maintenance panel so Evil does not escape.

Trivia

 * They are one of the first characters to have been made, the other 2 being Endo-Headless and Spring-Endo
 * He is the only character to almost always have at least one red eye visible, be it a dot or an actual eye