Just got all the units and maxed all xp. I see a lot of people commenting on the lack of use of the hero in later stages, and this is because the hero is just a loss catalyst, not a one man army. You need to all forward with your army and leave the hero parked at that start, and the rest is just picking the right accessories and the right units for the various challenges, like a good General does, and oversee victory from safety. The only trial I found challenging was the Golem, who pretty much oneshots everything, so the answer lay in the Hobbits, Goblins, Vampires, Mages, Succubi, and Witches. This gave me enough ranged dmg to burn the Golem boss down while kiting slowly back to the start. The rush of my cannon fodder goblins and hobbits and vampires slowed the golem enough to bring him down one last retreat from the start. Hope this helps.
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