|“||HUMM...THIS PLACE IS PRETTY BIG FOR A SINGLE PERSON. THIS IS KINDA SELFISH Y'KNOW?||„|
|~ Error!Sans after he ties up Cross|
Error!Sans is a major character in Underverse. With both him and Ink!Sans deprived of fighting each other, Error sternly tells Ink not to create anymore AUs and that he won't destroy anymore AUs. With the X-Event headed on its loose end, Error sees the truce he created did nothing to stop Ink, and ends it off shortly after his discovery.
With half of the multiverse gone, Error!Sans takes this tied battle as his own gamble against Ink. He forces Ink to abide by his truce of having no more creation and destruction.
One day, while waiting for Ink to come back, Cross is surprised by Error's appearance. He takes his soul, and once Ink arrives, Error tells him he can't save him. Telling him to stop, Error fires his blasters on Cross; Ink gets the hit instead when he frees him from Error's string. His soul, however, is now stolen, and with that, both Cross and Cross!Chara are fighting for control, leaving Ink injured.
After the fight against Cross, Ink is pulled over by Error, who alerts him that he still has Cross's original soul because of the truce, and bluntly tells him that he'll have fun if he finds out that he broke the truce.
While he takes a break from finding the Omega Timeline, Ink arrives in Error's world, telling him he had a long day, and needed a break before he overthrows him. The two watch Undernovela, but as it continues, Error notices that Cross has entered the AU, taking Undernovela!Frisk in order for Cross!Chara to have a human soul. Once Asgoro and Sins barge in to save the day, the two are met by Ink, who uses his vial to erase the pair. Ink gratefully thanks Error for joining his game, and as soon as he wakes up, he enters the Doodle Sphere and proceeded to tie up all the AUs.
He enters X-Tale when he glanced towards its page, not aware that Fresh had also made it here as well, protecting it from outsiders like him until Ink "comes back". While Fresh provided him the details that Ink had left for Underswap, Error is stunned by the fact that Underfell's Snowdin and Underswap's characters had landed in this AU. Knowing it was all Ink's doing, he officially proclaimed that the truce was over.
After Nightmare!Sans relocates himself, X-Event!Chara and Killer!Sans to Outertale, Error barges in to demand Ink's location, in which Nightmare redirected Error towards Sans and Outertale!Sans, also finding Ink. While he does fail to get them the first time, he gets Sans, Underfell!Sans, and Underswap!Sans the next time he strikes. His recklessness leads Ink to where Error was holding everyone hostage.
They immediately head to battle for the vial, but no one could stop Ink from dropping the vial, wich commenced the revival of XGaster. What happens next is Error's destruction of the multiverse, and his ultimate fate to be trapped in his own realm.
Before Xtra Scene 1, his appearance is similar to a Sans; his head is completely black, with blue streams running from his eyes, which his scleras are red, his comea are yellow, and his pupils are blue. His exposed legs are red, his slippers, pants, and jacket are in blue, yellow, and black, and his fingers are yellow. With the advent of Lucidia, he was redesigned to match that of Lucidia. His pants and jacket now feature blue stitches, and he now has a scarf, which Ink seems to like when he first encounters this design. Both designs feature the word "ERROR" all around him, with some minor glitching included.
Error!Sans can not only fire Gaster Blasters and summon bones at his will, but can shoot out strings called "Gaster Graspers" to tie up his victim. These strings can be used to extract the souls of the victim itself. He's even able to destroy AUs, and as of Xtra Scene 2, he is able to perform this feature due to the truce bring over.
Error may have a sensitive feeling towards others, but he's often shown to be remorseless, wanting to destroy all the AUs Ink cared so much. Even though the truce was made, Error still had a negative feeling with Ink, especially when he started talking about his new friend. He even extracts Cross's soul without Ink's consent, but he still decided to keep it intact to stay loyal with the truce. Once he makes the discovery, though, he feels confident that he'll beat Ink and destroy his precious AUs.
| X-Tale: Cross | X-Event!Chara | X-Event!Frisk | XGaster | X-Tale!Papyrus | X-Tale!Undyne | X-Tale!Toriel | X-Tale!Asgore | X-Tale!Asriel | X-Tale!Mettaton | X-Tale!Alphys