So here is the mental image I got.
Garth makes some sort of black magic ceremony that binds the “souls” of his army to make them the resentful spirits at death dragging the closest enemy with them.
Death and Decay
Orpal standing on top of a hill looking down at enemy troops and buildings. He raises his hand performing a spectacular magic curse. An atmosphere of doom is engulfing the enemey territory. It is so strong all the enemy units and heros are barely containing it, most of them already lost to immense pressure and started to rot and melt leaving decayed bones behind. Even buildings couldnt stand the intensity of this magic atomsphere they started to crack and crumble.
Think anime Bleach reiatsu (soul pressue) but more black magic-y and sinister.