The final battle has terrible balance; the armies are disproportionate, there are no artifacts left, and stats decrease (meaning there's no point in collecting stats from the map). I don't know how the author managed to complete it; I couldn't. The only dark spell available is from a scroll, but artifacts are taken away in the final battle... In short, I struggled for a long time and gave up. I wish everyone enjoyable gameplay on this version of the game:
https://www.youtube.com/watch?v=i4tnHO-3H6k