Mysa Nal of Naltor, sister of Dream Girl, is the Lady Legionnaire known as the White Witch:
Unlike her fellow Naltorians, such as her sister, Mysa was not born with the ability to see the future. To compensate, she studied magic on the Sorceror's World, and eventually joined up with the Legion in the aftermath of The Great Darkness Saga.
While she was a powerful sorceress, she was rather limited in that she couldn't spontaneously perfrom much in the way of magic, needing to memorize spells in advance, and only being able to keep a limited number of spells memorized at a time.
Like many other Legionnaires, she was one half of a rather mismatched pairing, having a rather deep romance which was, by necessity, chaste, with fellow Legionnaire Blok. A native of the planet Dryad, Blok was a silicon-based life form, possessing a massive, dense, stony body (hence the necessity for the romance to remain chaste).
Blok was so massive that while most Legionnaires could fly to soaring heights at great speeds with their Legion Flight Rings, he required several rings just to get off the ground, and generally could not keep up with the others.