How to kill Black Dragons?

If we remove the requirement for a "decent" troop, I'd suggest a harpy. Not for online play, of course, but it's not too overpowered. You can set it up, clear a small, enclosed area (4x4). Then, just let the auto-battle run and watch the show.

Here, the approaches are fundamentally different... How long will this "show" take? Against 15 Black Dragons? No one except a tournament offline player would be interested in that. Let's rephrase the question. I want to gain experience for these 15 Black Dragons, at least for one hero. :)

Don't suggest trapping a hero in a small, enclosed area under flight and letting a harpy attack. :-D

Why did I even get involved? I didn't understand the saves. Wanderer, please, reveal the secret - why did your Black Dragons start appearing in groups of three? Did you convert the saves from Equilibris?

You won't believe it, but some people don't use Whirlwinds at all. Only when absolutely necessary. Otherwise, they only use Equilibris.