Reboot

Reboot is the Swapverse equivelant of the Underverse's Error. As a direct contrast to Error, a black and red evil destroyer, Reboot is a blue and white friendly rebirther. He wears a black version of Sans' coat. He seems to have power over SAVEs. He travels the multiverse restoring universes destroyed by Ink. He is very friendly to AU citizens and creators alike. He still has a bad side however, and will become extremely frustrated if he catches ink trying to destroy an AU, usually leading to earth shattering battles. Due to them being evenly matched, the battles have varying results.

Note: all information past this point is assumed based on information from the original Underverse, and may not be definitely canon.

Going off of his coat and the backstory of Underverse's Error, he likely used to be like an Aftertale version of Disbelief Papyrus. He then "Rebooted" himself into his current form, and tries to reboot other universes so they can have the happiness he lost.