Demon invasion.

Updated the campaign file, made changes to mission 4:
1) Fixed a bug with the Cave Lords;
2) In several places, the guard has been weakened, and the growth of the number of some neutral creatures over time has been disabled;
3) The AI's armies have been slightly weakened;
4) Enemy heroes appear less frequently;
5) Guilds have been unlocked in the Inferno cities.

P.S. I left the trick for winning mission 3. Those who figured it out are clever.