Wolfsbane is a mutant who is able to transform into a wolf. As a wolf, her strength, speed, reflexes and senses are similar to those of a wolf's, but are also heightened beyond those possessed by a real wolf. She can see into the ultraviolet and infrared portions of the electromagnetic spectrum. She perceives things as patterns of heat, thus she can see things even in absolute darkness. She can hear sounds that are beyond the range of human hearing and can also detect scents that ordinary humans cannot, therefore she can trail someone by scent just as a wolf or dog can. Wolfsbane can judge a person's emotional state and detect any changes in that state as they occur through observing the heat patterns and scents that person gives off. However, she does not possess a wolf's instincts.

The story of Rahne Sinclair is a sad one. An only child, Rahne's mutant powers emerged during the culling of Scotland by the Horseman of Apocalypse known as Mikhail. Her parents attempted to hide her but failed. The young girl was discovered by Mikhail's hounds and brought before him alongside her parents. Mikhail made her beg for her parents' lives, making her pledge allegiance to Apocalypse. Through tears, she promised her life to Apocalypse. Rasputin thanked her for her pledge and reduced her parents to ash anyway. Unable to cope with these horrible actions, she reverted completely to her wolf form.

After that ordeal, she was shipped to the Dark Beast's labs. The Dark Beast took her on as a special project, believing that she could be his key to reverting from his bestial form to his human form. While a captive of the Dark Beast her feral abilities were pushed beyond their limits. For months she remained in her wolf state, never straying far from the Beast's side in his laboratory.

When Jean Grey infiltrated the Breeding Pens, Wolfsbane discovered the telepath and was knocked unconcious in order to prevent her from alerting her master. Jean loomed for a minute over the fallen beast, finding it interesting that there was a decidedly human psyche buried beneath the wolf's mind. During the final battle with Apocalypse, Rahne wandered the ruins of New York City in her wolf form. Discovered by Wild Child during an X-Men patrol, Rahne was brought to Magneto. With the help of the X-Men and Wild Child, Rahne was able to regain her transitional wolf girl form but was still unable to revert to her full human self. However, through counseling and great effort, Rahne was able to keep her animal side at bay.

When Magneto, the new government's Director of Mutant Affairs, unveiled the X-Men as part of his new plan to use mutants to hunt renegade mutants, Wolfsbane was on of the members chosen for their inaugural mutant raid on the Hellions at the Massachusetts Academy. After all the X-Men had done for her, she was happy to finally get a chance to earn her keep. Caught off guard, the Hellions were easily neutralized and taken into custody. The Hellion called Catseye almost made a clean getaway, but was discovered fleeing by Wolfsbane.

Her two closest friends in the X-Men would be Xorn and Beak. After Xorn appeared to be fatally wounded in battle against the Morlocks, Beak and Wolfsbane went to visit her in the infirmary. Beak was happy to report that the ones who had done this to her had been caught and were downstairs in holding. Wolfsbane thought they should go down and teach the Morlocks a lesson for what they did, but Xorn asked them to think about how they would react to strangers who seemed to be trying to take them back to captivity, having been trapped themselves in Sinister's lab not too long ago. They surely would have fought back against the X-Men as well. While Wolfsbane was aware of this, she was only trying to make Xorn feel better.

At a time when the X-Men were most vulnerable, Xorn revealed herself to be Paige Guthrie, a former member of the X-Men bitter at the team at having left her for dead, and took Magneto's son Charles Lensherr hostage. She would pay for this trangression with her life, but revealed with her dying breath that Magneto was in league with Sinister. Wolfsbane felt betrayed when she heard this news. Magneto told them he was trying to catch Sinister and here she found that Magneto had actually aided him, keeping him free to continue his experiments on other victims like she had been. Rogue was quick reassure Wolfsbane that, despite Magneto's action, she would never have to worry about Sinister again. Subsequently, the X-Men would hunt down and kill Sinister and Magneto would confess to the public that he had been decieving them. In spite of what had transpired, Wolfsbane remained with the X-Men.