A mighty fun campaign. In my opinion, it's more like a learning by doing tutorial, which forces you to carefully evaluate your units, carefully analyze and pick your troop setup, and so on.
You can easily fool around to get a higher level, for all I see. Lore found it out, and good work. However, it does take a lot of fooling around and a lot of digging. There are plenty of upgradeable items though... With level 3 learning and hand of necropolis (it spawns) you can get to a higher level, but it's all the same. This is the next campaign where level 5 units own everything when properly utilized