onedreamer
Dragon
You can also think that to balance out the slavery thing, a slave should appear only if a unit was successful at attacking (not at defending).
Or if you want slaves to be even more rare, they could be generated only after a city has been conquered/razed, x slaves could be generated depending on the population of the city.
Or if you want slaves to be even more rare, they could be generated only after a city has been conquered/razed, x slaves could be generated depending on the population of the city.