Merlin

Merlin was a wizard during the reign of King Arthur in Camelot during the 6th century. He possessed a demon of immense power called Etrigan, which gave him many magical powers.

History
Merlin had foretold that the King of Camelot would be able to remove Excalibur from the mystical stone. Arthur was the man that removed the sword from the stone, and he became the king of the British nation, and he gathered his Knights of the Round Table. Merlin served as the King's court magician. When a time traveling Superboy arrives in the 6th century, Merlin is jealous of Superboy's great powers. King Arthur even states that "[Superboy's] magic is greater than thou!" Driven by jealousy, Merlin and the Black Knight scheme up a plan to get revenge against Superboy.

Meanwhile, King Arthur tells Superboy that if he has the strength to remove his sword from an anvil, then he will become the king. He easily removes the sword, but then Merlin uses his magic to remove the sword from Superboy's hand, and gives it to the Black Knight. Superboy humiliates the Knight and easily defeats him. King Arthur then tells the Knights to seize the Black Knight and Merlin, but Merlin uses his magic to teleport away.

Although showing himself to be a very villainous individual, Merlin was apparently not all bad. Many centuries later he became a member of the superhero team known as the Freedom Force. He teamed up with Isis, Hercules, Super Samurai, and Sinbad for many adventures at the Valley of Time.

The demon that he possessed named Etrigan was eventually passed on to a man named Jason Blood.