His title, "Demon King", is not to be confused with that of one of the previous villains, King Piccolo (Piccolo Daimao).
Dabura is first seen when Goku, Gohan, Vegeta, Piccolo and Krillin are led to Babidi's spaceship by Kibito and Supreme Kai to aid them in preventing Majin Buu's awakening. Babidi and Dabura are aware of their hiding place in the mountains nearby and, as it takes a massive amount of energy to awaken Majin Buu, Babidi decides to use theirs; Dabura is ordered to kill all but Supreme Kai and the strongest three and lure the remainder inside the ship. Dabura obeys and quickly charges the group and, with a single blast, kills Kibito; he then leaps in the air and spits on Piccolo and Krillin, turning them to stone, before retreating back into Babidi's ship, telling the brave Saiyans to trapse into their domain if they dare.
Dabura joins Babidi in a monitoring room and watches as first Vegeta easily kills Babidi's henchman Pui Pui and Goku then destroys Yakon before Dabura himself emerges to confront Gohan. When first encountered, Goku mentions that Dabura's Power Level is comparable to that of Perfect Cell. Though initially it seems that Gohan and Dabura are even, Goku corrects himself and states that Dabura might be more powerful than he thought, with his usage of magic and several tricks.
During his battle with Gohan, Dabura takes notice of Vegeta's poor temperament and his one-track mind for settling things with Goku. Dabura then retreats from the fight with Gohan in order to inform Babidi; Babidi quickly takes advantage of that information and possesses Vegeta, when this was actually what Vegeta wanted all along, so he would gain a greater power and finally defeat Goku.
With Vegeta now battling Goku (after refusing to kill the Kai and Gohan, saying they're of no interest to him), Dabura stands with Babidi to fight against Supreme Kai and Gohan. Before they can start though, they are all shocked as the energy released in Vegeta and Goku's battle has already been enough to release Majin Buu, as both fighters were fighting at Super Saiyan 2, the form thought to be the pinnacle of Super Saiyan states at the time, rapidly landing colossal amounts of damage.
When Majin Buu emerges, Dabura is disappointed, as it seems the fat being is nothing more than a useless imbecile. Majin Buu overhears this remark and attacks Dabura, quickly gouging him in the eyes and then kicking him into a mountain, leaving him broken. Dabura does manage to recover somewhat though, and throws a magical spear through Majin Buu. He tries to convince Babidi that Majin Buu is uncontrollable and should be contained again but Babidi refuses to comply, and then tells him that he was nothing more than a pawn, and like all pawns, regardless of his loyalty or efficency, should be tossed away when not needed anymore. Majin Buu then retaliates against Dabura under Babidi's orders, turning him into a large cookie and eating him.This in turn reverses what he did to Piccolo and Krillin, restoring them to normal.