Wolf, also known as Woe or the Wolf King, is an aging black wolf bearing a distinctive red scar across his left eye and possessing a muscular build. He inhabits the mountains near a sheep farm, governed by a strict belief in nature's law: survival necessitates killing. He declares, "In order for some to live, others must die," describing his world as "a hell where death is always close by." His predatory actions stem from this philosophy, with some versions implying he consumes his prey.

One night, he attacks a sheep barn, slaughtering multiple sheep including the mother of a lamb named Chirin, who attempted protection. Chirin subsequently seeks revenge. Wolf dismisses the lamb's initial challenges. Chirin instead requests apprenticeship to gain strength. Despite knowing Chirin's ultimate goal is his death, Wolf reluctantly accepts. Over years of harsh training across wilderness and mountains, Wolf mentors Chirin in survival and combat, forcing confrontations with predators like bears and panthers, and pushing him to develop physical prowess such as ramming through trees and shattering boulders. During this time, Wolf's initial dismissiveness softens; he develops genuine affection for Chirin, viewing him as a surrogate son and taking pride in his transformation into a formidable, horned ram.

Later, Wolf leads Chirin back to the original sheep farm for a final test, instructing him to slaughter the flock. Chirin kills the guard dogs but hesitates upon seeing a mother sheep protect her lamb—mirroring his own past. When Chirin refuses, Wolf intervenes, provoking a confrontation. Chirin impales Wolf with his horns. Mortally wounded, Wolf expresses gratitude and pride, acknowledging death in battle as a fitting end for a wolf. He states, "I always knew it would be like this, that I would die in some feud, at the hands of someone stronger. But I'm glad that the one who did it was you... Chirin." This outcome implies Wolf may have trained Chirin harboring a subconscious hope that his apprentice would grant him a warrior's death, especially as he aged and grew less capable of hunting alone.

Wolf's core character remains consistent across most adaptations, though nuances appear in his relationship with Chirin. The original storybook depicts immediate apprenticeship acceptance, while the film adaptation shows greater initial reluctance and gradual bonding through events like Chirin's failed attempt to save a bird's eggs from a snake. His design and role are otherwise unchanged, maintaining his identity as a force of nature shaping Chirin's tragic arc.