Other nifty new features include the alternative upgrade patch for units, the ability to retain your heroes, selling artifacts in the marketplace, collecting special artifact sets (hey didn’t Diablo do this a few years ago?) and sacrificing troops for experience. This last bit is nice if you’re trying to quickly race up the level tree, but most players will likely find that keeping peasants around as cannon fodder is more useful than a small experience boost.
The alternative upgrade allows you to choose from two different upgraded creature types when training new troops in town. This extra level of differentiation offers a bit more flexibility when designing an army for battle. If you end up with creatures of the wrong type, you can return to town and swap one upgraded type for another.