Merlin is Arthur's counselor and magician, and in many ways, he is the prime architect of Arthur's reign: Merlin helps Uther Pendragon to become Arthur's father; he guides Arthur to withdraw Excalibur from the Stone; he is the creator of the Round Table and prophet of the Grail; and he helps Arthur attain various goals. Even with all his magical power, however, Merlin has some weaknesses. He becomes infatuated with Morgan Le Fay, the half-sister of Arthur. After teaching her the tricks of the trade, he is imprisoned by her. In other versions, Merlin is enchanted by Viviane.