4 separate realities, each with various differences and quirks. When Yellow from the original timeline messes up something with Command Blocks, he accidentally creates some alternate timelines. He, Green and Purple are sucked into one of the realities and they must find their way home, but they aren't prepared for the foes and friends they will meet in this timeline...
The 3 alternate realities where the groups come from will be fully explained when we get there, but for now, the names and groups:
The Beckerverse (Green, Purple, Yellow)
Powers, Powers Everywhere (Second, Blue, Victim)
A Peaceful Resolution (King, Chosen, Animator [in stick form whaaaaat?])
The Red Defenders (Red, Dark)
(if you're reading this, hi, i'll add a cover later)
(TW: unaliving thoughts and memories at the beginning. It gets better over time, don't worry! Trauma is difficult to overcome...)
You didn't want a second chance.
You didn't want to survive.
You wanted the sweet release of death.
But it seemed like the universe was far too cruel to allow you even that.
It took away your memories, your free will to choose whether you live or die...hell, it took the one thing in life you owned! Your own name!
And now it seemed like you had to live yet another cruel life, doing things you never wanted done to others. But...at least you could do things your way.
Maybe this second chance wouldn't be so bad...
(Reincarnated as Nightmare Sans, but unlike other stories, you have no clue what Undertale even is)