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.