Deadwalkers are rotting hunting packs and hordes of mindless walking dead.
Ever since the Realm of Shyish came into being corpses have stired from their graves and corpse piles upon the battlefield. Unguided and without thought, the dead wander and as the wars grew so did the rotting herds and proccessional, gaining new members for all peoples and races. Animals large and small also awaken into unlife with the most common being the dire wolves, foul remanants of once sleek hunting packs and the greatest being found in the ranks of the Beasts of the Grave. 
All the great powers of Nagash use the Deadwalkers, Deathmages find them easy to raise and control whilst Soulblight vampires expend them without thought, preserving their more prefered followers and minions. Necromancers construct corpse carts, stinking chariots of death pulled by the dead and either boosting the powers of mages aligned with death or disrupting the sorcerers of others.