When Jean Grey was believed possessed by a cosmic entity known as "the Phoenix Force" she was given infinite telepathic and telekinetic powers. At first she used those powers for good as Phoenix. Later, the power overwhelmed her and she went mad and destroyed an entire star system and billions of lives. She transformed into the "Dark Phoenix" and became the X-Men's most bitter enemy. Only the love of Cyclops could get Jean to reassert her human side long enough in order for her to sacrifice herself to save the universe. The ultimate conclusion of the Dark Phoenix saga seen in Uncanny X-Men #137 was one of the most traumatic, unexpected events in the history of the X-Men. Fans throughout the world today still debate its ramifications in heated discussion and arguments. One thing is for sure: the Dark Phoenix Saga is one of Marvel's Greatest Moments!