Demon invasion.

The campaign is great; there's no denying that. I don't see the point in rushing through the maps and completing them quickly just to get badges. It's much more interesting to explore everything, level up to the max, equip your hero, and defeat everyone without exception. I played through the campaign once, and it's interesting that in one of the maps with orcs, I found the ability of archdemons useful – they pulled in an enemy centaur, and the elder demons finished them off without exposing themselves. It's usually a rarely used ability, but it came in handy for me. I'll find the save file and add it.