Dark Ranger

Dark rangers are elven rangers with a different focus. The dark ranger is a cunning hero, adept at manipulating opponents. Forcibly raised from the dead, the former rangers of Quel'Thalas enjoy nothing more than sowing dissension and hatred within the enemy ranks When Sylvanas Windrunner, Banshee Queen of the Forsaken, regained her physical body, she realized that the natural world would never respond to her wishes again. Angered by this development, she turned to the arts that were becoming more and more natural to her: Necromancy. She altered her elven ranger teachings into a new form. Thus, the dark rangers were born. When the Lich King's power began to wane, his mental domination was weakened, and many of his undead became free of will again. Many undead elves including the dark ranger Sylvanas, found themselves free of will, and Sylvanas rebelled against Arthas, turning her banshees against their former king. After gaining control of the Tirisfal Glades, Sylvanas proclaimed herself Queen of the Banshees and leader of the Forsaken (the free-willed undead).

Many dark rangers are former banshees. The difference is dark rangers have regained their physical bodies, thus possessing greater powers.

For more information on Dark Rangers, see:

http://www.wowwiki.com/Dark_ranger