New era.

I completed the Sigrif scenario on the same day and finished the final one today. In the end, I didn't give up on Chaos; instead, I abandoned the education path and focused on Darkness. Overall, I used Subjugation and Vampirism a few times. Otherwise, I defeated him with Chaos. I got the Boots of the Earth, so Meteor Shower dealt 2-2.5k damage, and with luck, it dealt 5k. He had protection against everything except Earth; his general protection reduced Earth magic damage. I passed it on the first try, but I lost Minotaurs and Witches (I was unlucky, and a Berserk was cast on the Witches, and then they cast it on the Minotaur, and they killed each other, haha). I also lost Beasts, but it was just by chance. Overall, I thought it would be difficult, but it turned out to be quite easy.
To make it more challenging for him, he needs to increase the army growth slightly. I had more Dragons than he had Devils. He had more of all the other units, but he had fewer Lords than I had Witches. That's why I quickly captured the town with Witches and Dragons.

Regarding the final: I initially tried playing as Askh, and I easily defeated the Necromancer, but Urgash is invincible for Askh. I also made a mistake and only later realized that I could assemble an army of 6-7 units. Unfortunately, there were no racial Dragons there, which also affected the battle. I critically lacked resources for the Mentor; Darkness didn't drop until the very end, so I started with a not-so-great build. But I think Urgash can't be defeated by Askh, at least not with the native Elven troops.
I tried playing as Urgash and easily killed both of them without any losses. Chaos is just too overpowered. And the Imps drain all the mana in two turns (and I killed everyone in three turns). Urgash is officially overpowered. Maybe I'll try playing as Askh again sometime; I won't play as the Necromancer, I don't like Undead. And he's objectively the weakest there, although you managed to complete it, I saw your screenshot, but I don't feel like trying it.
Thank you for the trilogy! You have the best maps! Although "Elemental Equilibrium" is also a great map; if it had a difficulty level like yours, I think it could compete as a single-player scenario.