Ben, Gwen, and Kevin travel to the center of a water planet, namely Pisces, Ripjaws' home planet in an attempt to find Aggregor. They end up getting help from Magister Pyke, one of Ripjaws' species. The planet has a 2% solid core, which holds an instrument that holds the planet's water together in a gravitational pull. Aggregor takes the instrument and reveals it to be a piece of The Map of Infinity. As the planet is pulling apart, Aggregor escapes. Ben transforms into Goop and uses Goop's anti-gravitational UFO in an attempt to fix the centripetal force holding the planet together. Goop vanishes, and Kevin says he was atomized and spread throughout the ocean. The water then turns green, and Goop pulls the planet back together.
Spoilers ahead. Coverage follows the scope labeled below.
Complete story — includes the ending
Ben, Gwen, and Kevin are summoned to the aquatic planet Piscciss (Ripjaws's homeworld) by Magister Pyke, a Plumber who reports that Aggregor has been sighted near the planet's solid core. Ben and the team pursue Aggregor and reach the planet's center, learning that the second piece of the Map of Infinity is disguised as a gravitational device which is responsible for holding Piscciss's liquid atmosphere together. Aggregor steals the piece of the map and flees, causing the planet to come apart; Ben transforms into Goop and uses his antigravity device to replace the map piece, which stabilizes the planet's atmosphere. While Ben and his team are celebrated by the people of Piscciss for saving their world, they lament that Aggregor has once again escaped from them.
Sources and content license
Source and revision history · Adapted from Wikipedia contributors, List of Ben 10: Ultimate Alien episodes. HTML formatting and reference markers removed. · Content license