Proceed to the Scarlet Crusade's base camp between Felstone Field and Dalson's Tears and destroy their command tent. Place the Scourge banner at the camp, and then return to High Executor Derrington at the Bulwark, Western Plaguelands.
Before Andorhal, we must tackle the advancing Scarlet Crusade menace from Hearthglen. They've made camp between Felstone Field and Dalson's Tears, making us risk conflict against both the Scourge and the Crusade at once.
My plan is to play them off of each other by sending you to destroy the command tent they've set up; use some Flame in a Bottle from this box of incendiaries. Once razed, plant this Scourge banner by the tent. With some luck, they'll ignore us and focus on the Scourge for vengeance.