A long and complex scenario.

In my opinion, the most challenging scenario is the fifth mission of the fifth campaign ("Ranger") - "The King's Sunset." All the initial conditions are initially in favor of the computer, making the beginning very difficult. Furthermore, Nicholas's army is much larger than Faelan's, and he recruits it faster, so you have to resort to all sorts of tricks. A lot also depends on luck.

The original game isn't very suitable for playing as demons in this campaign. I can suggest downloading the "Flame of Vengeance" campaign from the All4heroes.net website, where you can play as Biara. It's a campaign for the "Tribes of the East," so there's a mentor available. Plus, it simplifies obtaining a super ability.