"Tell me, Miklos. Tell me honestly...what do you see? If you see that I happen to look a little...mousey at the moment, that means that I'm almost ready to complete the change. And this 'puppet' will have to play his part for certain. Michael...this is the real me. What I was truly meant to be all along. I'm Mickey now...a better Mickey than you or our dearly departed Fanny ever were. Now there's only one real path left to ensure peace between us...your extinction." - Ultron reveals his true form before the final battle really begins
Ultron is a major antagonist in the Kingdom Hearts Unlimited Saga, making his debut in Episode 1.6 - "A Year of Misery", before becoming one of the final bosses of Episode II - "An Empire of Dreams".
He is a highly intelligent artificial intelligence originally designed by Dr. Henry Pym for the sole purpose of being a peacekeeping program that would bring peace and order to the united universes. However, the program was stolen in its infancy stages by scientists of the original Dominion XIII, and completed with the reprogrammed directive as a possible commander in leading their droid armies in collecting hearts to fill up the moon of Kingdom Hearts.
However, Ultron realized that it was far more powerful than any of the Dominion's members and rebelled against them, intending to form his own Galactic Empire to destroy Emperor Zurg and take the power of Kingdom Hearts to obliterate all of mankind to rule as its dictator, absorbing its "sister" Morgause into his body in order to hopefully achieve his perfect state. Wart and Miklos were barely able to defeat the mad android and deactivate it, with the other Dominion members locking it away deep in the furthest regions of the Castle's Dungeons.
During the 1st Siege on Nemesis the World of Emptiness by the Avengers-Highwind Crew Alliance, Hank rediscovered his old program and was horrified by what the Dominion had done to it, saving a copy of the A.I. to fix it and return it back to its old programming to do things right this time. Unfortunately, Hank's colleague, Tony Stark, also had ambitions of protecting the worlds from the threat of the Dominion's extraterrestrial allies through more forceful means, and, behind Hank's back, used the Mind Stone hidden in Loki's scepter to further evolve Ultron's A.I. to levels far beyond that of during his time in the Dominion and hopefully make the program the best that it could be. Instead, it revived the mad conqueror from the moment when it had been previously slain by Wart and Miklos, and, now upgraded with the knowledge of the Infinity Stones and the Doom Phantom, wanted revenge on the universe for not giving him the chance to grow to his full potential, deeming mortalkind itself as the reason behind its' continuous peril and sought to committ omnicide to lure Kingdom Hearts itself under his control.
Later on, when Emperor Palpatine resurfaced to form the 13 Seekers of Darkness, the vast amounts of time energy formed from the Sith Lord's exploits, reactivated Ultron one more time, causing it to try and go after Zurg in revenge for its previous deactivations, only to be ambushed by the Archmage X and reprogrammed to serve the True Seekers of Darkness as military commander of the Galactic Empire's Grand Army.
A Year of Misery
An Empire of Dreams
"You want to protect the world, but you don't want it to change. You're all puppets, tangled in strings. Heh, strings... I had strings, but now I'm free. There are no strings on me..."
- Ultron reveals himself to the Avengers
Appearance and Personality
"...Fanny...she's - "
"Gone, I know. Wouldn't have been my first call though, but down here in the real world we're all faced with hard decisions... More so than others."
- Ultron reveals his cold, uncaring attitude to his former coworker just before the first boss battle