Here's what happened.
The opponent capturing two Castles on day 4 or 5 shocked me because I only managed to take a gold mine and one Castle by day 5, and the second one on day 8.
I placed the Birds on day 7, and things started to go pretty well.
I broke through the border on day 141, and the first battle took place the next day.
All 6 Birds that I had at that point were thrown into the fray, but I won the battle, although the opponent retreated with his last Druid. We decided to continue the game and play cat and mouse. To be honest, I made a mistake here and rushed to finish him off, without even taking care of immunity. As a result, I lost the second battle because the main trump card – a Necromancer with excellent single-target spells – was quickly killed due to the lack of potions. After that, I was driven out of his territory, but the next day, I stocked up on immunity potions and, taking Harpies for speed, rushed back. I think there was another battle in which I also managed to win and push the opponent back into his territory. Soon after, I took one of his Castles (Life), and then the final battle took place.
My army:
Level 11 Barbarian (melee) + Level 1 Order (accuracy)
Level 8 Sorcerer (3 levels of Chaos, lightning, and area-of-effect spells)
Level 11 Archer (ranged) + Level 1 Scouting (I couldn't make a Ranger:( )
Level 7 Necromancer (3 levels of Death, dispel) + Level 1 Warfare
Level 9 Sorcerer (3 levels of Chaos, lightning)
6 Harpies and 2 Crossbowmen:D
My morale was definitely in the negative, but it didn't bother me; on the contrary, since my troops moved in the middle of the round (either after the enemy or before him if he waited), I calmly used the Necromancer + Chaos Sorcerer + Archer combination to methodically eliminate the enemy heroes, while the Barbarian provided cover and destroyed the enemy army that approached my mages.
After destroying the Priest and the Warrior, the opponent announced his surrender:)
Thanks for the game!

Барон "Vampires"
Отдай свои прошлые сны,
В сомненьях себя обрети,
В бешеном танце душа кружится!
Не думай, что будет потом,
Здесь и сейчас мы живем,
Стань хоть на миг сам собой, слышишь!