The Z-Warriors follow the Supreme Kai to the hidden underground spaceship of the evil wizard Babidi, who plans to use Gohan's stolen energy to resurrect an ancient, planet-destroying monster known as Majin Boo. Babidi uses his dark magic to possess the latent, lingering darkness inside Vegeta's heart, transforming him into the ruthless Majin Vegeta. Desperate to settle his lifelong grudge, Majin Vegeta challenges Goku to a brutal, no-holds-barred duel, completely ignoring the looming threat of the monster's awakening. The immense energy generated by their violent, prideful clash inadvertently fills Babidi's energy meter to maximum, causing the sealed ball to crack open and unleash the bizarre, unpredictable Majin Boo upon the world.