Wart is the main antagonist of Super Mario Bros. 2. He is an evil frog who wants to conquer the land of Subcons by using the monsters he created by messing with Dream Machine, which is used to create dreams. Although he doesn't appear physically he plays a minor role in the lore of Worst Hero And Villain War Ever.
Worst Hero and Villains War Ever
Wart was one of the first monsters created by the hatred of Angel of Darkness. He managed to conquer a world in Videoland known as Subcon with the help of his nightmare monsters. Somewhere in his reign he had a son who he wanted to become his heir. Wart was eventually defeated and vanquished thanks to a rebellion started by the Mushroom People. After Mushroom People took over the Subcon was renamed to Mushroom Kingdom. He would lose his half-frog half-turtle son during the rebellion, but the son would be raised by the Koopa Clan, who would make him their king.