Heroes of Might & Magic III: Horn of the Abyss

A castle with only high-level creatures is a terribly bad idea. In the early game, even a single angel purchased there will dominate, and in the late game, 7 units of level 7 (with the "Spirit of Despair" artifact, which can be found on a random map in almost every other tile) will create such a severe imbalance that the opponent won't be able to handle it and will hit you over the head with a chair. As a result, multiplayer will soon disappear, leaving only a depressing single-player experience.