This is a version of Error!Sans was plucked from his original AU by a Multiversal Being called Fate, and were manipulated by the deity to destroy countless AUs to preserve the balance of the Multiverse.
The multiverse started out with only one universe, that being UnderTale. Finding it too empty, Fate created her "true child", Ink, to fill the emptiness. She whispered to him lovingly, telling him that there was limited space and he could create, but only up to that limit if he didn't want the multiverse to collapse. When he ignored, forgot, or didn't hear her warning, he went on a creating spree, filling the multiverse to a dangerous point.
When too many universes exist at once, they get crammed together in the limited space of the multiverse and continue growing until the eventually bump into each other and pop. Like bubbles in a container. Fate adores Ink, and fails to reach him or to make him stop his behavior. Instead, she pulls Error out from an early, forgotten AU of Ink's that hadn't collapsed thanks to Error. She puts him in the Anti-Void and, remembering her previous mistakes, screams his purpose at him. She never stops the screaming.
Error is corrupted by Fate and his memories of his AU are as well. He is tortured, not only by Fate, but by the other AU residents as well, when he is subdued for a while. His limbs are ripped off, he is poisoned, his rib cage is crushed, his bones are shattered, and he is hated by most in the multiverse. Destiny, the sister of Fate, takes a liking to Error. He is then her "chosen child" and she begins to formulate a plan to have him escape the bonds of Fate. For while Fate is all-encompassing and controlling, Destiny is by your own design. All it takes is one small action to change your Destiny. She only hopes that he doesn't break along the road to changing it.
The multiverse is largely aware of Error's existence and all Sans equivalents gather with the Star Sanses to discuss a new battle strategy. Many Sanses from the Original AUs(as opposed to copies of those) had previously caught Error and attack on sight. They then proceed to terribly injure him--repeatedly--until he is able to escape. He is considered an insane destroyer who enjoys his job by the "good" Sanses. The "bad" Sanses, as in Nightmare's gang and others from violent AUs, enjoy his company and know that he is forced the destroy universes for the Balance between creation and destruction. Ink doesn't know about this balance, and plans to create an empty AU and attack Error with all of the AU Sanses he can gather.
Error, falling for this trap, heads to the empty AU and is ambushed by too many Sanses to count. He is beat down and ganged up on but cannot die because of Fate pulling her strings as usual. While Reaper engages him in close combat, all the others fire their blasters at once. Error throws Death out of the way after telling him that they are both a part of a balance. Error is suicidal at being told he is unwanted and unneeded, and once the smoke clears, he opens a portal to the VOID below him. He was flaking off dust but still didn't die, and decided that, for once, Fate will not be in control. He would go against Fate. Fate who needed him alive and all the others who wanted him gone. He went straight into the void, hoping to be scattered across space and time. Instead, Destiny put him back together and handed him off to another multiverse to heal. One that would put up a fight for him--Warverse,
FGoD Error or Erratum is very similar to Canon Error minus a few details. For one Erratum is among the tallest Sanses, standing at 9ft(274cm). He is also covered in poorly treated scars and ashy bones due to lack of self care.
Erratum's tear marks look more like tears then they do on Error. On versions of him the marks are untouched by scars. Even if they seem to cut right through the tears.
Erratum is strong both psychically and mentally but is very socially oblivious. Often not understanding why people worry about him they way they do when he talks about himself. Tends to talk about his trauma not knowing it's going to affect people.
Like Canon Error, Erratum holds a strong love for Undernovela and Outertale.