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In general, I killed Zidar in two stages. In the first, the task was to drain his mana so that he wouldn't have enough spell points for Armageddon or Clone. In this scenario, he hasn't learned any other magic yet. The idea during the battle was for the Titan that had finished its attack to immediately engage the enemy Clone, but in the video, things didn't go exactly as planned, but the task was accomplished: Zidar didn't have enough mana for casting in the second battle. It's also important to have the Ring of the Mage so that the antimagic on the Titans lasts until the end of the battle. After that, Gundula enters and kills Zidar. Sandro is the least useful of all the heroes, so he was sacrificed. Then I bought him back in the Necropolis at point 79.0.1.
P.S. I forgot that Gundula's Executioner is a basic unit.
https://www.youtube.com/watch?v=eXQSbT2FKKE&t
https://www.youtube.com/watch?v=HmCys6g2jTg
Added 4 minutes ago
But after completing the walkthrough, I had some thoughts on how to kill him more easily: on the grass, immediately after exiting the one-way passage, without sacrificing a hero. But this plan needs to be tested. We take harpies, stacks of ifrits, a scorpicore, and a devil into the army. The scorpicore should stun the Titans. During these three rounds, we cast Prayer, Blessing, and finally antimagic on the harpies. Prayer on the devil will give him a speed of 11, meaning he can kill the Titan Clone every turn and also drain mana. It's important that Zidar doesn't hit him with Armageddon or kill him with the Titans. This is a potentially weak point.
P.S. I forgot that Gundula's Executioner is a basic unit.
https://www.youtube.com/watch?v=eXQSbT2FKKE&t
https://www.youtube.com/watch?v=HmCys6g2jTg
Added 4 minutes ago
But after completing the walkthrough, I had some thoughts on how to kill him more easily: on the grass, immediately after exiting the one-way passage, without sacrificing a hero. But this plan needs to be tested. We take harpies, stacks of ifrits, a scorpicore, and a devil into the army. The scorpicore should stun the Titans. During these three rounds, we cast Prayer, Blessing, and finally antimagic on the harpies. Prayer on the devil will give him a speed of 11, meaning he can kill the Titan Clone every turn and also drain mana. It's important that Zidar doesn't hit him with Armageddon or kill him with the Titans. This is a potentially weak point.