The Conqueror's Challenge can be issued by a member of one planetary civilization in order to challenge another for the rule of both worlds. The Conqueror's Challenge was developed by the Galvan as a means in reducing the massive destruction caused by interplanetary wars. In a Conqueror's Challenge, ordinarily issued by the invading species, members of each species can choose a single warrior to represent them in battle. The winner of the battle then becomes the ruler of both planets, while the loser is banished from the invaded planet forever. The rules of the Conqueror's Challenge are outlined in the Galactic Code of Conduct and ratified by the Casey-Kelly Accords.
Vilgax was one of the most successful conquerors in the Milky Way Galaxy, dominating ten planets through his combat abilities alone. In Vengeance of Vilgax: Part 1, he successfully defeated Ultimos and conquered the planet T-K, and issued another challenge to Ben Tennyson of planet Earth. However, in Vengeance of Vilgax: Part 2, Ben defeated Vilgax, who was subsequently banished from Earth. However, Ben did not become the ruler of Vilgaxia after winning the challenge.