Okay, I'm currently struggling with Phantom, before this fight was easy, there were fewer Enchantresses and their stats were higher.
What mana/unit losses would be considered acceptable? It will be problematic to keep the units alive. For this, you need to roll a sequence of good casts. I found a fairly stable drop rate for Slow + Prayer, and that's what I'm playing with. But I also need a Shield drop in the next Djinn cast.
In the first successful attempts, all Enchantresses and 30 Archdevils are preserved.