Complete story — includes the ending
In the Eastern European monarchy of Zarkovia, Prince Gyula reveals to his father, King Xarion, that he has acquired the corpse of Dr. Viktor, and intends to weaponize it to crush internal rebellion in the country alongside Gyula's mind-controlled army. Xarion, fearing the prince, summons Ben, Gwen, and Kevin to remove Dr. Viktor from Gyula's custody. Gyula confronts them and unleashes Viktor, who is under his mind control, who quickly defeats and captures the trio along with King Xarion. Gwen helps Xarion escape, but Xarion betrays her and drags an unconscious Ben into his lab. Using AmpFibian, Xarion transfers his mind into Viktor's body, becoming "King Viktor," a virtually unstoppable weapon. King Viktor attacks his son and unleashes his wrath on the rebels, but is attacked and defeated by Ben, Gwen, and Kevin. However, they are unable to take King Viktor to the Null Void due to the Plumbers not having the authority to arrest Xarion. Gyula declares that he will hang King Viktor, but Ben frees Gyula's army from his mind control so that they can choose their own sides, then leaves the country with Gwen and Kevin. Ultimatrix alien debuts: Wildmutt (cameo) Heatblast (off-screen activation)
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