The corpses around the death walker were those of the many beasts and the few humans that had died recently. So most of the corpses were from beasts.
They corpses of the beasts were mostly from those who died in the earlier explosion and the beasts who are currently dying in the tunnel that they have made and the beasts dying to the flamethrowers below and the beasts dying to the guns from above.
So the death walker had a lot of corpses to work with. This continued to be the case as the battle dragged on.
With a single divine ability, she became an entity walking amongst the dead and every living being close to her became too close to death for comfort. She had embodied what it meant to be a death walker.
The corpses of the beasts rose up from the dead and began to fight their comrades. This reduced the number of the defenders quickly and made the humans begin to gain an advantage in terms of numbers.
