Obtain a Fel Reaver Power Core and a Fel Reaver Armor Plate, then bring them to Blood Guard Gulmok at Shadowmoon Village.
We can't allow the Legion to trample us on their march to Black Temple.
Find a way to destroy the infernals they intend to use against us. That's not a request, [player]; it's an order.
The Fetid Pool near Legion Hold holds an old fel reaver power core you could use as the basis for a kind of fel bomb. Search the other wreckage near the fel reaver for a section of armor plating. You should be able to make a bomb powerful enough to take out those infernals and give the hold a nice shake!