Xgaster

His appearance bears an X strap around his coat and shirt, and a belt with an X strap around his pants. During his time with the determination he gained from XTale!Frisk and XTale!Chara, his appearance in Underverse is a semi-melted version of his real self. Thanks to X-Event!Frisk, he has no legs, which doesn't matter as he can still float around to move.

Near the end of Timeline X, he begins to melt due to the excess determination in his body. Throughout Season 1 of Underverse, he holds this melted appearance. Once he regains his original soul, he stops melting, though not without changes to his original body. In his Corrupted form, he has a sharper grin, narrower eyes, claw-like hands, and glitches where his legs once were.

Personality XGaster is more of a mysterious character, showing his isolation to the main characters except in special times, such as when XTale!Sans attempts to murder XTale!Frisk on stage. He's also a very clever man; knowing that everyone would soon revolt against him, he took his own soul and handed it to Ink for safekeeping.

Despite this, he shows much more borderline sociopathic and abusive tendencies towards his children, seeing them more as "experiments" than anything else. He barely cares about anyone's else feelings, and only wants them to fall into his own hands, using them as a puppet to his advantage.

The closest thing He has to a Redeeming quality in the modern day is his friendship with Ink, but even then he isn't above manipulating him.

The Animated prequels display that he was once a genuinely kind being, simply wanting to make a perfect world for his children. However, as time went on he shed every redeeming quality he once had and he became more and more cruel as he grew more and more desperate for his "perfect world". He even displays several signs of outright sadism, finding the anguish his sons had after he killed Asriel and Asgore "exciting," and then after brainwashing Frisk into a killer, he mocked Chara, saying "Frisk wants to play with you".

He is also shown to be extremely obsessed with control and shows several traits of narcissism, ranting about his kids for fighting back, accusing them of being "ungrateful". He also calls the other universes that aren't his own "garbage". This all shows that beneath his stoic, calculating demeanor he is mentally a child, seeing his universe as a toy box. XGaster is a major character in XTale and Underverse. He is the sole creator of the XTale universe. XGaster had lost complete motivation towards creating a perfect world, but after his visit by Ink!Sans, XGaster invests more time to creating "the perfect story" for his universe. This motivation causes tensions, not just within his own universe, but to many others soon afterwards.

Xevent