He didn't have any Light Magic, but he did have Summoning Magic, which was completely useless in his situation (I took it because I thought it was essential for an elf, and that he would summon his own troops, like in Heroes 4).
He also had almost useless Chaos Magic, and a bunch of almost useless skills, except maybe Enchantment, which came in handy.
Despite the almost thoughtless hero development, I usually managed to get by at the "warrior" level... But not in this mission.
I didn't really focus on tactics either, and mostly relied on ents and dragons, not really caring about archers and druids in battles.
In general, I couldn't kill Koly on my first attempt, nor on my second, or even my third,
even though I already knew about the dragons and phoenixes... After that, I went to the forums for information, in particular here, and read about 10 pages, and it was all so familiar :)
I also read about tactics on the LKI page, and realized that I needed to protect the archers, and that it was best to divide the druids in half, starting with 30, and that it wasn't necessary to upgrade unicorns and ents right away, not to mention dragons, which could be sacrificed for free slots for druids.
At the same time, I downloaded a save for all the open Campaigns and, ignoring Koly, I completed 2 missions as a Mage, but Koly still wouldn't leave me alone, he was almost in my dreams :) I finally decided to take care of him myself.
I started playing very seriously, spending almost half an hour on each game day. I decided not to collect artifacts to get Phoenixes,
because I had already done that before, and I wanted to go a different way, i.e., to kill all the Spectres (which I later regretted).
I also thought about developing a super lucky Talanar or Dirael, who has Light Magic, but it didn't work out.
In general, while I was killing the Spectre dragons, I also had to defeat all these Ravenns, Orsons, Vlad, and others, as well as Koly himself, about three times :)
In the end, I lost all 300 archers that I had accumulated, because I couldn't resurrect them :(.
When, after killing the last group of Spectres, I killed Koly again
(and I chased him out of the Orange Castle, where he was holed up with a decent army, but I had more than 100 Ents...),
and he still didn't die, I almost gave up. Some kind of glitch...
By the way, there's another glitch there - the Experience Tree in the Necropolis territory, you can't get to it in any way,
I tried to do it for two whole game days, but it's not every day that you can get to level 30 for free :)
But I couldn't...
In general, I went to collect the damn artifacts, and many more game days passed before suddenly a message appeared,
hinting that now it was possible to kill Koly. After that, I finally killed him on the second try :)
Moral: collect artifacts, get Phoenixes, and kill the bastard without unnecessary hassle.