Lycanthrope

Lycanthropes are humanoids or giants who can transform themselves into animals. In its natural form, a lycanthrope looks like any other members of its kind, though natural lycanthropes and those who have been afflicted for a long time tend to have or acquire features reminiscent of their animal forms. In animal form, a lycanthrope resembles a powerful version of the normal animal, but on close inspection, its eyes (which often glow red in the dark) show a faint spark of unnatural intelligence.

Since the Menace of the Underdark expansion, Lycanthropes exist in DDO with the introduction of Werewolf monsters.