Ultimate Sacrifice.During a battle, Ben transforms into Ultimate Humungousaur and suddenly declares that he is not Ben, attacking Gwen and Kevin. The two subdue him and consult a psychologist about his behavior, who deduces that he is suffering from some kind of split personality disorder. Ben screams and vanishes in a flash of light, leaving only the deactivated Ultimatrix, which Gwen realizes Ben is trapped inside of. Gwen and Kevin are divided on how to rescue him; Gwen uses an astral projection to enter the Ulimatrix, while Kevin travels to Galvan Prime to seek the aid of Azmuth. Kevin reaches Galvan Prime and battles a Galvanic Mechamorph security system, yelling at Azmuth that Ben is a hero and his best friend. Azmuth, moved by Kevin's growth and maturity, agrees to help him. Inside of the Ulimtatrix, Ben encounters his ultimate forms, which claim that they possess their own lives and minds, and wish to kill Ben in order to free themselves from him. Gwen arrives and saves Ben from the ultimates, and the two pursue them to a fiery pit, which the ultimates demand Ben jump into in order to liberate them. Gwen threatens to destroy the ultimates, but Ben tells her to stand down, and realizes he must sacrifice himself so that the ultimates may live. Ben kisses Gwen and hurls himself into the fire; he regains consciousness outside of the Omnitrix, where Azmuth, Kevin, Gwen, and the ultimates await. Azmuth reveals that he has repaired the glitch that granted the ultimates erroneous sentience, and says that the Ultimatrix recognized Ben's sacrifice and freed both him and the ultimates. Azmuth agrees to take the ultimates to a planet where they can live in peace, and Kevin offers to buy food for his "best girl" and his "best friend."