Hey there fellow readers!
Before we start with the "Swap!NorrustlerRoam story", there is something I must resume first.

Just as I showed in Fell!NorrustlerRoam's backstory, that is pretty much the same until the part where Nightmare first gets bullied and that Error got created around 40 years after Ink, thanks to the latter that created 90.736.187 AUs in 100 years.

The first three days of getting bullied, Nightmare doesn't say anything but Dream guesses that something bad is going on, unfortunately for the smaller, he doesn't have specific proof and Nightmare refuses to say anything, even with Dream's constant questions about the subject.

On the middle of fourth day, Dream comes back from the village very early from the planned time and notices his brother being bullied. He interferes, but one of the bullies hits him with a brick, causing a huge fracture on Dream's skull.

That was the first time that Nightmare so furious. He ate only one dark apple, just to make him able to create a shield and a weapon against anyone; it was also the first time that Nightmare attacked back other people, so that made everyone wary about coming closer to the tree.

The fracture caused Dream to reduce his mentality and erase part of his memory. Nightmare suggested to eat a golden apple but that didn't change the situation of the dreamer. He had to relearn a lot of stuff and Nightmare became more protective of him, they were almost glued to each other.

The "older" twin told Dream everything bad that the villagers have done, he warned that if any of them came closer to the tree, they only meant to hurt him so Dream was scared to leave Nightmare alone and he himself was afraid of being alone as well.

A few months turned into a couple of years, Dream slowly started to recover a little more of his former self but it wasn't at its fullest. During that time, Ink came to visit Dreamtale.

From a far away distance, he noticed the guardians, and concluded to use one of them as his own pawn. He saw Nightmare as the problem to fulfill his plan, the purple eyed skeleton was more smart and knew almost everything that was good or bad, making him a really hard target to steal.

Dream, however, a sarcastic thanks to the damage made by brick, he was more manipulable and naive. Easy target to use as he pleased. Ink waited for Nightmare to go up to the tree and created a clone of him to trick Dream, which succeed.

After catching Dream, he turned him into stone and stole him from Dreamtale, and before that, he left a small blood trace to trick Nightmare into thinking that the villagers kidnapped Dream.

When Nightmare found Dream missing and the blood on the floor, he was blinded up in more rage than before and ate all the black apples with the sole purpose of destroying and killing everyone on the village, because he was sure they took away his brother. When he literally destroyed all the AU and never finding his brother, Error appeared and told him about the balance, the Creator aka Ink and a lot of more stuff, that's when the theory of his brother being taken by someone outside of the AU came to his mind, but it was already too much late because a lot of AUs were created and it would be impossible to find him so quickly.

Meanwhile, Ink took advantage of the "statue-like" state of Dream and inserted a spell to damage his memories more than they already are. Around 500 years later, the smaller skeleton was freed from his statue prision and began to be used and abused by the Creator to do his dirty work.

On one of the "dirty work" missions, he met his brother which he didn't recognize nor did Nightmare recognized him at first. They fought for half an hour, until Nightmare used a tentacle to hit Dream's head and after receiving the hit, the golden eyed skeleton yelled "Don't hit my head! They threw a brick at me and I lost my memory once already!", that made them both stop the fight, frozen in place.

That's when Nightmare stared and analized the smaller's face and body, gasping at the realization that he was his little brother who have been missing for 5 centuries. Dream gasped as well when some sense got into him and realized that he had been sent to kill his own brother, the very own brother who taught him everything. The dreamer couldn't look at the eyes of the taller skeleton after what he had done and ran from the AU.

They randomly encountered each other but did nothing except stare for a few seconds and then leave. During that time, Dream met a few friends that managed to help him recover more his mentality, but still was considered a kid/child, side effect of the huge hit from his childhood who didn't healed enough and the secondary accidental hit from Nightmare.

Blue realized that Dream was being manipulated and brainwashed by Ink, but before he could tell to any of the Bad Guys or Error, he told Dream about Ink's true behavior and nature, not realizing that it would cause a huge problem in the future.