Activate the Eternal War Unholy Manifestation on Skarbrand's army.Move both of your armies as far South as you can without marching.Research Serial Killing in the Technology Tree.Demolish the Kennels in Infernius and build a War Amphitheatre.Move your new Bloodreaper South to try and catch up to your army.Move Skarbrand as far South as possible and choose Daemonic Portal stance, recruit three Bloodletters of Khorne.Raze the settlement with Blood for the Blood God.Move and attack The Brass Glacier (best to manually fight to preserve your army).Attack and destroy the enemy Gharhar army (try to manually fight).