For fun on the first map of the Burdened Imp campaign I turned all my units and prisoners in the torture chamber for a pure ghost army.
With 70 lvl 10 ghosts you can 1 shot all enemies with drain using call to arms :P
Also not that for 71 ghosts I had a payday of 8000. Also if I would not be able to pay I built them a huge temple which they automatically visit so they will become happy again automatically
this is what happened