Use the Lorehammer to travel back in time and face the North Wind as Stormhoof. When Stormhoof falls and drops the Horn of Elemental Fury, recover it, finish off the North Wind, and then return to Xarantaur at Camp Tunka'lo.
1x True timeline restored
At last, we have all that we need to right the wrongs of the North Wind and its followers. You have attuned the Lorehammer to Stormhoof's time and his persona.
Take the hammer again, head to the Temple of Life in the plains to the northwest. Use the hammer to assume the role of Stormhoof. Face the North Wind as Stormhoof, but realize that for the timeline to be restored, Stormhoof must die as the North Wind weakens.
Then, you must seize and use the Horn of Elemental Fury to destroy the North Wind.