Walkthrough
Mission 1. I didn't attack some of the units at the beginning, but I returned to them later, after I had gathered all the reinforcements.
Mission 2. The start is very slow, but after developing to Ents, the game progressed faster. I cleared the neutrals with archers and Ents, using light magic. I took the trophies so that I would have enough resources for both cities. Later, I received darkness from the mentor and bought a tome in the shop. I quickly created a rain of Berserkers with a Masterwork Amulet.
Mission 3. At the beginning of the mission, an Orc helped a lot; after that, Cyrus handled everything himself. He used light and darkness magic (as did Alex). Alex, with Sandro's Cloak and a full set of Gnomes, won the battle against Saahir with one unit of Titans without any losses.
Mission 4. No one had a full set of dragons at the start, but it could be assembled immediately by combining the artifacts of Alaron and Cyrus. Therefore, the main strategic task was to arrange their meeting. I gave the set to Alaron, and he won all the battles against the heroes, with the help of dragons and vampirism. In the shop on Cyrus's territory, I bought Sandro's Cloak and solved an interesting logistics problem: how to quickly transfer it to Alaron, who was at the other end of the map at that moment. I didn't bother looking for the Tear. I defeated Lorchith without losses with one unit of dragons.
Mission 5. I played fairly and didn't equip the full dragon set. I won without problems for Alex and Alaron. In the battle for Cyrus, two units of Demonesses appeared immediately, and I was afraid that they would shoot down my entire army. I considered the options, like in a chess puzzle, and managed to play in such a way that they didn't even fire once (I didn't want to waste a turn on distraction). As a result, Cyrus had the fewest losses.
I rate the Campaign positively. All the maps are detailed, the plot is excellently revealed in the cutscenes, and the characters are vividly portrayed: Alex with his lofty ideals, Alaron, who constantly lacks determination, and Cyrus, who only thinks about personal safety and gain. Of course, it is important to separate the plot and gameplay here: in my Walkthrough, the alliance turned out to be gray in the sense that the heroes are formally on the light side, but they use dark magic more than the demons and Necromancers combined. If we talk about balance: there were comments from other players about the low activity of the enemies and the overall difficulty of the Campaign... but personally, I think everything is fine. Yes, the enemies don't attack on their own, and there is no risk of losing, but it is interesting to play, there are many battles against strong neutrals, and you get pleasure from exploring the map and gradually strengthening the heroes. I also remember the combat scripts in the fifth mission; I didn't check if the summoned units are fixed, that is, whether Cyrus always gets Demonesses or if it can be different?
I took the pictures from the fifth mission; the heroes are shown on the day of the final battles.
Thank you very much for the excellent Campaign!