Play against Necropolis.

Well, that's a big question – whether it will work or not. Spells are very powerful; even Cyclops can easily wipe out Knights. And Necropolis isn't like Haven; their defense is the second most important stat after spell power, plus they have a skill that boosts it (though I don't know if players focus on defense when playing Necropolis, I'm not an expert on that faction). So, they can definitely (in my opinion) withstand the first attack until the hero's turn.