“Flight to Salvation” – “Deeds and Paths of Darkness” [4th campaign, 1st mission]

Hmm, I just completed this mission on Veteran difficulty yesterday. There's nothing you need to bring from your own faction. I just did it in two stages. I killed the main city of the Dungeon faction, then went back a bit to get reinforcements and defeated it a second time, which was much easier (the main thing is not to be stingy with summoning golems). Then, I went left and around to the remaining castle. At the top, near the portal, there was a battle with the main army. I won with THREE ballista towers (some joined me along the way). After that, I quickly brought hydras and stalkers from the nearest castle, and that was it – victory.

I didn't use any mini-arts at all. I simply didn't return the main hero to the Academy castle. All the necessary spells from the self-cast spells were found in the Dungeon faction's castles.
Skills: Education into Mentoring, Expert Summoning, Expert Logistics with Pathfinder, Basic Luck, Expert Sorcery with a 20% discount on spells.