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 Messengers), 60 archliches, 5 phoenixes, and 52 high druids.
So, I'm running around with Faidaen on the western island, having previously captured one Undead Castle, looking for the second Castle and Kolya. I find a two-way portal at the very edge of the map, enter it, and... I end up on the northwest island, right in front of one of the two remaining Undead Castles. At the entrance, there was a mage hero with a tiny army. I defeat him and attack the Castle, and, believe it or not, Kolya was sitting there 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 don't bring the phoenixes into the battle. My druids and archers first eliminate 267 skeletons, and that's how the battle began. I, with Faidaen (level 29), take out their supply cart, and after 11 turns, Kolya's skeletons stop shooting. Faidaen had the "Mana Burst" skill - I used it to take out 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 watch the "Nicholas's Death" cutscene, and I get the message "Mission completed," and that's 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 have phoenixes (they don't necessarily have to be brought into the battle).
4) Catch Kolya by surprise, as in this case.
5) It is desirable not to miss such an opportunity as to use 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 messengers) in the battle, and heavy cavalry, and, if there is room, flying creatures are also very useful.