Ink!Sans

"Ignore these two, they're just weird clones that will die soon."

Ink!Sans is the main protagonist of The Truce and Underverse, and the protector of all AUs alike. He originally made a truce with Error!Sans to never create another AU again, so that Error won't destroy his other AUs. Later on, he meets XGaster in X-Tale, and he gracefully shows him the multiverse. It is suspected that XGaster would later on give Ink his soul within a white vial.

He later makes friends with Cross, who is devastated over the loss of his universe. Once Error!Sans takes his soul, however, Cross!Chara escapes to take Sans's souls without Ink's constant. The both of them, along with Underfell!Sans find their way to get Sans's soul united, but once that's solved, a new issue would challenge him and the AUs.

The Truce
In the prequel to X-Tale, Ink and Error are in arguing fights against the multiverse. Error is even more pissed when he finds out that the "multiverse" sheets he ripped were fake. As they begin their fighting, they're both teleported to a mysterious island. None of them can use their weapons, and none of them can actually leave. They're soon sucked up by whirlpool, which takes them to their own worlds.

After a long moment of time, Error!Sans and Ink!Sans are able to get back to the island with their own weapons back. They soon become "friends", allowing them to leave the place, and they both make a truce: Ink cannot create a AU, so Error cannot destroy the others.

He soon heads to another universe that was about to be destroyed. To his surprise, he meets XGaster, with his kids X-Tale!Frisk and X-Tale!Chara. XGaster wants to destroy his soul, citing his failures to make something perfect for his children. Once Ink shows XGaster the multiverse, he's motivated enough to experiment on his AU.

Before Underverse
XGaster shows Ink his newest experiment: the Overwrite function, which will allow him to change everyone within the timeline. Ink goes along with this, wanting to support his friend.

Not long before X-Tale was destroyed, XGaster also gives Ink his soul in a vial, knowing that someone might take it for his own.

After X-Tale is corrupted, Ink would later meets Cross, and by visiting him, he effectively helped Cross control Cross!Chara. The effort was ruined when Ink told him that he couldn't bring back his world, and it only got worse once Error!Sans takes their soul, giving them hours to live. Ink was severely damaged from the wreck Error gave him, and Cross escaped, now under control of Chara once more.

0.0
After Cross was successful in taking half of Sans's soul, Ink showed up and spray-painted all over Cross!Chara's face, telling him he'll never find happiness in Sans's world. Cross!Chara tells him to get lost, to which both him and Sans successfully trap Cross!Chara up. They escape though, with the intentions of creating their own universe.

0.1
Ink tells Sans everything regarding Cross, and asked if he wanted to go help him. Sans would decline, and he went off with his picnic. Then, out of nowhere, while observing Cross's universe, Dream!Sans shows up and warns him that his brother has made a deal with Cross, which Ink will take advantage to find him and stop his little plan. Once he hears Sans calling, he comes out at the wrong time, which Sans is confronting Frisk over resetting. Sans explains to Frisk, and tells him to look after him while he and Ink are gone.

0.2
At the Underfell universe, Ink tells Sans to wake up, where he's surprised by the appearance of a Snowdin. Once he figures out where he is, they both run off to find Cross, but are delayed by Sans's constant glitching, and when Cross is impaled, Sans feels the same way. They finally arrive at the scene, which Ink is displeased over Cross's own deed, and when Sans tells Ink that he'll handle this, Cross stabs Underfell!Sans with a hacker knife to take control of him.

The four battle it out; Ink ends up making a wall to stop Underfell!Sans's Gaster Blaster attacks, and once Sans freezes him, Ink holds on to Underfell!Sans with goop hands. These don't sustain itself, as they break free from his clutches. Once Cross evacuates from the area, Ink tells him to leave as well, saying he's not safe here. Before he could continue, he's taken in by Error.

Xtra Scene 1
Hanging, Ink tells him to put him down, which Error does so. Ink is surprised over Error's new design, which he's annoyed at. He shows Ink the soul that Cross originally had, saying that because of the Truce, he couldn't break it, but said that if he found out that Ink was indeed in league with The X-Event, he'd really give him a huge dose of consequences. Ink leaves his place, paints Underfell!Sans's tear so he can disguise better, and waits to hear from Dream!Sans on where Cross is going next.

0.3
After Underswap!Chara accidentally trips over Underswap!Sans to drop a canister of paint, Ink was able to float out of the paint to appear with Sans and Underfell!Sans. Ink suggest to all of them that they should wait, saying that it'll allow them to find Cross a lot easier, though no one took his advice. Once Underswap!Sans suggested that he's in the city, they all head there. With no surprise, Cross is already starting to destroy much of the city. Ink tells him that the code in Underswap reminded him much more of his original universe. He apologizes that he couldn't bring back his own world, and before Cross could attack all of them, Underfell!Sans's and Sans's surprise attack knocks him out.

With his soul reunited, Ink tells Sans that it's time to go home, but with Underswap!Chara too close to Cross!Chara, they end up reviving him back to his standard form. He's grateful to see Ink once again, which got Sans's attention, but he and Underfell!Sans are both knocked to X-Tale as Ink, Underswap!Papyrus, and Underswap!Sans both managed to stay in Underswap.

Attempting to stop X-Tale!Chara, he's tied up by Nightmare!Sans, and struggled to get out, as Nightmare feels his negative feelings. X-Tale!Chara congratulates Ink on showing him the multiverse, and once Nightmare lets go, he asks for his white vial, which he declines by kicking it away from him. He ends up battling Underswap!Papyrus and Underswap!Sans, but both are reverted as the battle progresses. Throughout the episode, Ink doesn't seem to do much so, with Dream!Sans even noticing that he couldn't feel anything from him. When Dream!Sans tells everyone to head to Outertale, Ink still doesn't budge, and Underfell!Sans pushed him in the universe anyways.

Xtra Scene 2
He appears later again in Xtra Scene 2 with Error, recuperating from the events that happened. As the two continue to watch Undernovela, Error notices Cross!Sans and Cross!Chara, and only then does Ink shows up and erase Asgoro and Sins with his vial of his. He thanks Error for champing into their game, to which XGaster points out that he needs to wake up from his dreams. Error would later find out X-Tale!Chara's carnage and accuse Ink for the mess, proclaiming that the truce was over.

Appearance
Ink has a brown cape that wraps around his neck, a tan-colored shirt, a brown vest with straps, brown shorts, a jacket around his waists, his paintbrush, and finally a strap featuring all of his emotion vials, including the white vial XGaster told him to keep.

Abilities
Ink!Sans can summon objects within his paintbrush. For example, in Underverse 0.2 Part 2, he brings up a giant ink wall to protect him and Sans from getting hit. He's able to morph into a ball, teleport through liquids, and turns what he has throw at the victim to become an object (e.g. Ink turning the paint he threw at Cross!Chara into chains).

Behavior
In the long run, Ink!Sans is generally optimistic, has a sense of kindness, loves making art, and can get too excited even to the point of throwing up ink. In the more serious side, he object tries to reason with anyone, and only follows what he finds his best friends. However, he has no soul, and relies heavily on emotion vials. This proves to make Ink unable to do any task at all, as shown in Underverse 0.3 Part 2.