Planktonamor is the main antagonist in the SpongeBob SquarePants episode Dunces and Dragons.
Planktonamor was the medieval ancestor of Plankton. It was revealed in the prophecy that Planktonamor wanted to rule King Krabs' Kingdom. He sends a dragonfish to kidnap the king's daughter, Princess Pearl, whom he planned to kill unless the kingdom was surrendered to him. The prophecy also revealed that SpongeBob and Patrick were the only ones who can stop Planktnamor, so King Krabs sends them off to save the day.
Later, the Dark Knight fools the castle guards into letting them in by pretending to torture SpongeBob, Patrick, and Squidley. After climbing a very high flight of stairs, the four manage to rescue the princess and engage in combat with Planktonamor. They are soon attacked by the dragonfish, but just when all hope seemed lost, SpongeBob managed to become friends with the monster by feeding it krabby patties. Having made amends with SpongeBob and the gang, the dragonfish burns Planktonamor, reducing him to ashes. The wizard then says one last line "Curses! You win.".