Nightmare is the final and third main antagonist and an enigmatic, dark animatronic in Five Nights at Freddy's 4. He could be seen as the Bigger Bad of Nightmare Fredbear, as while Nightmare Fredbear serves as a nightmarish version of Fredbear in general, Nightmare serves as theSPECIFIC Fredbear that bit the child's head. He replaces Nightmare Fredbear as the main antagonist on the final night, aptly named "Nightmare" (FNAF 4's 20/20/20/20 mode).
He is clearly based on Nightmare Fredbear, being some sort of demonic version of the already demonic looking Fredbear. Unlike Fredbear, his skin is translucent, exposing all of his animatronic parts. Upon closer examination, a black mass resides in Nightmare's head, theorized to represent the Child's bitten off frontal lobe. (citation needed)
He is black with a yellow hat and bow tie, the yellow hat having a black trim on it.
Five Nights at Freddy's 4
Just like Fredbear on Night 6, on Night 7 and Night 8, he takes the same role, appearing at 4 AM, and replacing all animatronics, taking up their duties. He must be handled the same way, but Nightmare is more aggressive than Fredbear. Also, he always directly appears at the doorway. Upon being attacked by him, he will appear in a screen similar to Golden Freddy instead of a complete animation. His existence is unexplained, and his purpose is unknown. He is acknowledged in the gallery as a separate entity from Nightmare Fredbear, meaning that he must have some sort of significance.