Ranger - "Higher Vampire" [5th Campaign, 5th Mission]

I had this idea: I captured 4 out of 6 Undead Castles, and gathered a solid army from all the Castles: 438 skeleton archers, 9 emerald dragons, 89 master archers, 34 death knights (a.k.a. Death Harbingers), 60 archliches, 5 phoenixes, and 52 high druids.
So, I was running around with Faidaen on the western island, having previously captured one Undead Castle, looking for the second Castle and Kolya. I found a two-way portal at the very edge of the map, entered it, and... ended up on the northwest island, right in front of one of the two remaining Undead Castles. A mage hero with a tiny army was guarding the entrance. I defeated him, attacked the Castle, and, believe it or not, Kolya was inside with a significant army: 1544 skeleton archers, 356 ghosts, 80 plague zombies, 46 higher vampires, 23 archliches, 12 death knights, and 9 spectral dragons. I didn't put the phoenixes into the battle. My druids and archers first eliminated 267 skeletons, and that's how the battle began. I, with Faidaen (level 29), took out their supply cart, and after 11 turns, Kolya's skeletons stopped shooting. Faidaen had the "Mana Burst" skill - I used it to eliminate the archliches, who were cursing my soldiers with their spellbooks. On average, Nicholas's army lost 5-6 archliches for each spell they cast + I finished off the archliches with death knights after my army destroyed everyone except the archliches and skeleton archers (it was a problem that I killed the archliches with the death knights, and the skeletons were standing right next to the archliches). The skeletons easily killed the remaining 4 death knights and started walking towards my archers. While the skeletons were walking, my archliches, archers, and druids destroyed the skeletons, and the battle was over. Then I watched the "Death of Nicholas" cutscene, and I was told "Mission completed," and that was it. It took me 3 months, 3 weeks, and 7 days. In the battle with Nicholas, the main thing is:
1) Faidaen must fight him.
2) Faidaen must be at least level 25.
3) Faidaen's army must include phoenixes (they don't necessarily have to be put into the battle).
4) Catch Kolya by surprise, as in this case.
5) It is desirable not to miss such an opportunity as using the troops of the captured cities. It is better to take skeleton archers, because there are many of them, archliches - they both shoot and cast spells, there should be death knights (death harbingers) in the battle, and heavy cavalry, and if there is room, flying creatures are also very useful.