Butchers are the servants of Nekrobiotek, tasked with everything from dismembering corpses to preparing them for reanimation. If it is dirty, dangerous and unpleasant, it is the job for a Butcher.
The Nekrobiotek are necromancers, surgeons and engineers all in one. They have harness the powers of magic to reanimate the dead and fuel the growth of the necro-industrial complex.
One way or the other, every army needs to refill its stock of corpses.