P.S. The map is designed for Darkness and Summoning (there are 2 types of summons)... I played as a demon/chose a mixed army (my native army couldn't handle it)... so, a strong leader is a must.
I quickly and aggressively took the nearby castles (losses are inevitable)... otherwise, the upper-tier mages will overwhelm you once you move into the dungeon. https://c.radikal.ru/c27/2104/43/0bdeaa7fb4c4.png