Seth

Seth is the prince of the Neo Kingdom and is a supreme sorcerer. He is also one of the many allies of Mario.

Paper Mario 4
In Paper Mario 4, he helped Mario defeat the evil king of dragons, Dragos. He used his magic to wear down Dragos' Defence, but it was not enough. So he decided to summon forth the Princess of the Stars, Rosalina to aid him. Although they defeated Dragos, Seth felt that this war was not over.

Paper Mario 5
In Paper Mario 5, Seth helped Mario defeat an evil spirit (who later was found out to be the evil spirit of Dragos) who possessed him. Even though they defeated this spirit, Seth sensed an even greater evil in their future.