Uninvited guests.

The question was about demons. It seemed that even with good tactics, a lot will depend on how lucky you are with the initial spells.
And, by the way, I didn't see anything about demons in the thread - Kahn is just very interesting in theory, but it seemed unrealistic for a "hero," maybe someone played successfully?

It turned out interestingly: the first half of your post is an answer to the second half. Kahn only looks interesting, but in reality, as rightly noted, everything depends on chance. In most cases, these random events will not give the player an advantage. How much benefit will there be if Kahn casts "Destructive Ray" or "Grief" for three units at the beginning of the game, while there are no ranged units among them? With Necromancers, you can't even theoretically rely on casting "Berserk" or "Subjugation." Demons look better in field battles. But on this map, the material advantage will always be on the side of the AI, and the main battles are the defense of your own castle, i.e., again, not in favor of the demon. In my opinion, Kahn can be useful when he reaches level 23-25; in the early stages, he is just a headache for the player.
Since no one has played as demons yet, you have the opportunity to be the first. Even if not on the most difficult level (if "hero" is unrealistic), but a well-reasoned review is always important.