The spell only works against heroes. It can be cast on bosses. Maybe give him immunity to mind control?

Added after 52 seconds

Yes, but the Dungeon lords still need to crawl to him.

There probably wouldn't be any problems with crawling. It's enough to reduce the enemy's initiative in every possible way and increase your own. And if the hero also has the "Surprise Attack" skill, then it's game over for all kinds of bosses) And it's unlikely that the boss would start attacking one Dungeon lord in the hero's army; he would most likely attack the Titans, as he did.

Added after 2 minutes
And I thought it was designed so that the hero would find all 8 dragon artifacts. They were added to me one by one after killing heroes. Some were even sold. I spent half the game just looking for the mantle.