Ranger "Refugees" - [5th campaign, 1st mission]

Exactly, at high levels, after the first battle in a week, the energy runs out and that’s it. Before patches 1.6 and 2.1, heroes had hordes of skeletons; 15% of the fallen would turn into skeletons without consuming any energy, and as a result, each battle would bring in hundreds of skeletons, leading to a massive number of them.