Ultimate Aggregor's History
In Ultimate Aggregor, it was shown that after Aggregor escaped the warehouse's explosion with Ra'ad, he traveled out into the desert to call his ship and transport him. However, he found himself ambushed by the Plumbers. Unfortunately, Aggregor was prepared and unleashed a torrent of laser cannons to bring down the entire ambush while he transported himself and Ra'ad to his ship. Just as he was about to make a jump to Osmos V, the lead Plumber of the ambush used one of the downed ships to take out the hyperdrive of Aggregor's ship. Unable to leave Earth, Aggregor had to come up with a new plan. When Ben and his team tracked his ship, they were attacked by Aggregor's robots but defeated them. When Ben, as Lodestar, boarded the ship, it self destructed, but Lodestar was able to survive with his magnetic abilities pulling him back together.
Meanwhile, Aggregor broke into Los Soledad with intent on using the Entropy Pump from Professor Paradox's old time-traveling experiment as a replacement for the machine on Osmos V. Upon discovering where he was, Ultimate Swampfire and his group stormed Los Soledad, charging through the remainder of Aggregor's robots. Needing more time, Aggregor used a Mind Control Headband to have the five Andromeda aliens attack them. Upon being freed from his control, Aggregor recalled the aliens. When the team confronted Aggregor, Kevin warned him not to go through with his plan, mentioning that absorbing energy causes Osmosians to go insane, while explaining his own acts in the original series. Aggregor however, refuses to believe it, claiming that powerful Osmosians told that to weak Osmosians to control them. Before Kevin could convince him otherwise, Aggregor used the Entropy Pump to transfer the powers and abilities of the five aliens into himself. Humungousaur managed to stop the pump before it destroyed reality. Unfortunately, it was too late as Aggregor had completely absorbed the five aliens, transforming into his mutated state, a massive chimeric mutant, named Ultimate Aggregor.
In Map of Infinity, Humungousaur became enraged over being unable to save the Andromeda aliens that he viciously attacked Ultimate Aggregor, demonstrating every ounce of his incredible strength. Unfortunately, Humungousaur's attacks did near nothing to Ultimate Aggregor. Showing off his newly acquired powers and abilities, Ultimate Aggregor toyed with Ben's team and easily defeated them all, greatly damaging Grandpa Max's nervous system in the process. After knocking Humungousaur out, Ultimate Aggregor left Earth.
Azmuth reveals that the reason Aggregor absorbed the aliens was so that he had the power to find the four fragments of the Map of Infinity, which will allow him to enter the Forge of Creation and obtain the greatest power in the universe. In order to stop him, Ben and the others must keep him from getting at least one of the fragments.
After going through a temple filled with booby traps on Mykdl'dy, Ultimate Echo Echo and the others nearly reach the first piece, but due to Four Arms and Kevin being forced to hold up the door that leads to the chamber holding the piece and Gwen being hit by a poison dart, they were powerless to prevent Ultimate Aggregor (who used the trio to discover the traps and lead him to the first fragment) from escaping with the first fragment of the map.
In Deep, Ultimate Aggregor invaded the core of Piscciss to steal the second piece of the map, which was in the form of the planet's anti-gravity generator. With the ocean planet falling apart, Ultimate Big Chill had no choice but to save Piscciss and let Ultimate Aggregor escape.
In Where the Magic Happens, the trio chased Ultimate Aggregor to the Door To Anywhere, which Ultimate Aggregor used to enter Ledgerdomain. Gaining the assistance of Charmcaster, the trio entered Ledgerdomain. When the group was in a battle with Addwaitya, Ultimate Aggregor used it as a diversion to attack Addwaitya from behind and steal the Alpha Rune from him, the third piece of the map, before thanking Ultimate Humungousaur for helping him and teleporting away. With only one more piece left, Ben becomes more determined than ever to stop Ultimate Aggregor.
In Perplexahedron, Ultimate Aggregor travels to the Perplexahedron, which was built by Paradox to protect the fourth piece of the Map of Infinity. He uses the map's other pieces to enter the Perplexahedron and makes his way through it, where he encounters Gwen and leaves her to freeze in a snow room. He finally makes it to the fourth piece but has a battle with Ultimate Cannonbolt. Despite his best efforts, Ultimate Cannonbolt is beaten and loses the final piece to Ultimate Aggregor, who escapes the crumbling Perplexahedron, now able to enter the Forge of Creation. Despite losing the battle for the map, Ben and the others vow to stop Ultimate Aggregor once and for all.
In The Forge of Creation, Ultimate Aggregor attacks Ben, Young Ben, Kevin and Gwen in the Forge of Creation and easily defeats Gwen and Kevin, leaving the Bens to fight him. Ultimate Swampfire grows vines to hold Ultimate Aggregor in place while Young Stinkfly attacks him. Ultimate Aggregor breaks free and knocks down both Ultimate Swampfire and Stinkfly, who transform back to Ben and Young Ben.
Young Ben offers his Omnitrix to Kevin to absorb it and fight Ultimate Aggregor, but Kevin refuses and absorbs the energy from the Ultimatrix. Ultimate Aggregor enters a Celestialsapien egg and prepares to absorb the Baby Celestialsapien, but is stopped by Ultimate Kevin, who then attacks him and absorbs his powers, reverting Ultimate Aggregor back to Aggregor and leaving him unconscious. Though Ultimate Kevin, having gone insane from absorbing the Ultimatrix energy, was about to kill him, he is persuaded to spare his life by Gwen, Ben and Young Ben.
Sometime afterwards, Aggregor was taken into custody by the Plumbers before eventually being sent to the Null Void.
