Changes:
New questline to liberate the Ancient Evil
New (modified) creatures + 1 boss + 1 super-hero + 1 Ancient Evil
New part of the dungeon (Tomb of Darkness + Wandering in Darkness + Repository of the Abyss)
And a few other things
Regarding hardcore players:
Difficulty adjustment
Increased creature growth in enemy cities each day
Increased enemy army size after capturing nearby outposts (depending on the current week)
And several other changes.
Note that I did not test two things:
a) The behavior of the Ancient Evil after emerging to the surface (it may be more difficult/impossible to complete the game)
b) HARD mode (probably made it too hard)
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I will be glad for any comments and feedback, which I really need right now.
Sincerely.