Black Magician

The primary antagonist of the Maple world who threatened the world before the time of Altair Camp who had been defeated by Aran, Freed, and the three other unknown heroes. He killed Freed and sealed off Aran, Mir (Freed's Dragon) and most likely the other heroes for hundreds of years . Later Empress Cygnus started a new group of knights to assist in defending the world. As the main antagonist, his form as a monster would be pretty powerful. If your party can't beat Pink Been, they will surely not beat Black Mage.