I didn't have much money, and I played the entire game with only 5 heroes. I took a GOG and a couple of Imp lairs. On day 115, I captured a village, and on day 117, I ran into the opponent. There were 30 blue heroes and 4 demons, and I had 21 GOGs, 2 Ifrits, a Ballista, and higher stats. I killed 20 blue heroes, and they paid a ransom. The next day, they surrendered. Gundula "killed" her own hero, and the opponent decided not to continue.
Thanks for the game!