The most challenging campaign.

There are 2 of the most challenging campaigns, with fierce battles: level 3 for the Dark Elf and level 5 for the Light Elf; I completed everything on Heroic difficulty, except for the expansions. When I fought the Overlord, I was disappointed; there were many armies, and I leveled up my heroes to 30, but I was facing a bunch of demons, which was frustrating...