Underverse (originally called Underverse!Sans) is the animated series created by Jakei95 majorly connected to the X-Tale universe. It follows the story of Sans, and how one visit by an unfriendly face would mark the start of what was to be the greatest fight for the multiverse.
Ink!Sans may be happy-go-lucky, but when he's serious, he uses his paintbrush to summon various objects to defeat his foes. He helps the other Sanses throughout their journey, but he may be lying about his true intentions...
Created with the only purpose to compile all the data generated during the Timelines, as well as keep XGaster’s personal notes during and after the X-Event development. XGaster had all his trust on her until he discovered she was part of Chara’s rebellion in the 4th Timeline. Alphys was overwritten into a loyal and emotionless assistant. She is still able to think for herself, but she doesn’t want to get involved in trouble anymore and only focuses on obeying her creator.
He was always destined to grow up alongside his two human brothers and maintain peace between humans and monsters in the world created by XGaster. He never became Flowey. However, he can transform into his Exterminator version (Flowey X) with the Overwrite button. Asriel is XGaster’s favorite “weapon”.
XGaster never liked this creation, who always maintained the qualities of a kind man despite his miserable and lonely life, like in the other Universes. Now he’s only a being full of remorse and rage aware of the reality of the Multiverse.
She is aware of all the events that occurred in her Universe, the true fate for her son Asriel and her relationship with Asgore in the Original Universe. In her mind, she only keeps the memory of her loved ones smiling in a peaceful and happy world before everything went out of control. That’s why she refuses to open her eyes, fearful of forgetting that image and facing reality.
Muffet was the first one to encourage Chara to rebel against XGaster. After the events of the 10th timeline, she was overwritten into a killing machine. She can create illusions with her poison and stopping time.
She was the first creation who attacked her own creator. Now she’s his personal bodyguard along with Papyrus. All her happy memories with Alphys are fake. But deep inside her soul, she still has feelings for her. She doesn’t believe in justice anymore.
After absorbing 95% of Underswap!Chara's soul, X-Event!Chara regains the power to manipulate, control, and overwrite the code of AUs. He desires to take revenge for his suffering at the hands of XGaster.
When the X-Event initiated its training, it decided to use this resource and make him a robot with many qualities, the most outstanding being an unstoppable Royal Guard, an idea that gets XGaster’s attention and giving origin to the final concept for his perfect story. Mettaton has an insatiable appetite and always eats anything in his way. His favorite food is souls, both humans, and monsters'.
His kindness and optimism captivate everyone else, even getting to confuse XGaster. More than a simple creation, XGaster sees him as a closer relative, as he sees in him the innocent and pure side that he lost long ago. Papyrus feels great remorse and disappointment towards Cross after having been exterminated by him in the past.
Cross is the anti-hero of Underverse, conflicted in most of his actions. Cross desperately wants to bring back the world he lost by taking code from other AUs, but in reality, X-Event!Chara is the one pulling his strings. Now revived, Cross is currently with Dream and CORE!Frisk in the Omega Timeline.
Error!Sans is the deuteragonist of the series. While he did take Cross's soul, he didn't destroy it because of the truce he and Ink made. He wished the truce would end, something that would happen when he discovers something in X-Tale.
As the brother and opposite of Dream!Sans, Nightmare's goal is to spread negative feelings through the multiverse. He makes a deal with Cross, giving him the ability to access any AU he wants as long as he causes suffering in the process. He was last seen in the Doodle Sphere, attempting to kill Dream.
While Ink refuses to let him help find Cross, Dream does give the crew vital information by spying on the enemy. Dream is currently in the Anti-Void with Cross and CORE!Frisk, injured by his recent fight with Nightmare and Killer.
Nightmare's subordinate, pulled from his respective timeline to aid him and X-Event!Chara in their plans. He harbors a grudge against Chara after their alternate universe self forced him to kill. His role in Season 2 is currently unknown.
Comes from a timeline of Outertale. He has not met the Frisk of his timeline yet, and is just living a peaceful life with his brother. However, he soon finds sinister intruders and attempts to defend his timeline from them.