Sorrem at Furien's Post wants you to find the Ancient Summoning Ritual in Thunder Axe Fortress.
With his dying breath, Kohor mentioned the summoning of a demon that could threaten the entire region.
He may have been bluffing, but that's not a chance worth taking.
This cannot wait for the Horde's invasion of Desolace to take shape. You must scour Thunder Axe Fortress for clues and bring an end to this potential threat.