This information is based on alternate scenes or materials, and is not considered canon within the overall plot of the AU.
Shortly after Nightmare! Sans became corrupt, he created some "Nightmare! Papyrus" and they became mindless and obedient to Nightmare (without a mind of their own). The tree of feelings considered Nightmare might want a friend to keep him company while corrupt, so it shined some of its shadow on one of the clones before it fully formed, and it gained a mind of its own. It encountered Sans and referred to him as his "brother." Nightmare was at first skeptical, but after Nightmare Papyrus put a random local in a torture machine he invented, and Nightmare saw the massive radiation of negativity, he took Papyrus under his wing and made him the "true" Nightmare! Papyrus. After multiple more inventions were shown to Nightmare, Nightmare and Papyrus became pretty decent friends, as Psychopath Negativity-Incarnate skeletons go. He made many inventions to assist Nightmare, such as a Portable DTR Extractor (For Frisk-killing,) a Beam that absorbed positivity (to leave beings open to negativity-sucking,) and a Positivity/Negativity Apple-maker (to Corrupt people.)
Nightmare Papyrus acts similar to his Classic Papyrus counterpart while un-corrupted, rather than calling himself "The Malevolent Papyrus," He calls himself "The Extraordinary Papyrus." He still has the ingenuity and Intelligence of his corrupt counterpart. He is known for constantly spewing technobabble, much to the annoyance of his brothers. In the Non-Canon comic of a different turn of events, "Sans, I'm back." Papyrus is rejected by his brother, Nightmare! Sans. Causing him to become a Cold-Calculating Monster, using Inventions to Obliterate any trace of resistance to his rule. He still can build inventions in most interpretations of himself. While corrupted, he acts like a comedic sidekick to his brother, Nightmare! Sans.
Powers and Abilities
He can use his Negativity to generate whatever weapon he wishes. Normally he makes Bones and Blasters. He also makes a Nightmare Katana and forms tentacles in combat. He can use his inventions to obliterate his opponents, however, he only does this in specific circumstances, as he finds it to easy.
the two are good friends, and brothers. He doesn't really care for Sans, as he's the incarnation of negativity. However, they are still good friends nonetheless.
He often shows off his inventions to his brother, not exactly hate him that much. He only attacks Dream when ordered to by Nightmare.
The two are enemies. they often battle, and Nightmare! Papyrus uses his inventions to gain the upper hand. He seems reluctant to kill his brother, as they are still brothers. He is much less merciless than his brother, however.
- He has astraphobia, fear of Thunder/Lightning and neophobia, fear of clouds.
- He basically hates any weather than Sunshine, Ironically enough.
- He has a blind spot, similar to his brother. He can't see out of his scarred eye.
- He owns a dog named "Sir Nightmarish a-lot," who was an Outertale annoying dog that was fed an Negativity apple.
- He is the 3rd Youngest of the Four Brothers. (Younger than Dream, older than Dream!Papyrus).
- He created multiple theoretically Impossible Machines, such asana Atom-reformation Machine (Change a object into a different object), a Time Machine (self-explanatory), and a AU-Character-Generator (If you lack a character in your AU, you put DNA into the chute, and select a character, it combines your DNA with that of said character, and creates a variation. [E.x. if Alpha!tale Sans put his DNA in, and selected Frisk, it would make Alpha!Frisk]).