Play as Inferno.

I'm playing as Necropolis against, say, Axel. It's impossible to keep the game short because we're playing for a set amount of time. By the way, you definitely need to take Luck and Leadership, but Defense and Education are completely useless. First, about defense – it doesn't give the demon anything against Haven, because there are troops there in stacks. Here, as was correctly noted, you need to block the Knights. And concentrate on the Knights and Angels, and subdue/berserk/blind the rest, because the opponent will obviously cast Antimagic/Vampirism on the Paladins on their first turn. We attack with Gating, and protect our own troops. The Staff of the Underworld is a good item, must use. In general, you need more artifacts for Initiative. And definitely take the Amulet. You don't need to level up Intelligence, because it will block access to Spell Power, and we really need Spell Power, because of the sudden attack and instant reinforcement. Luck is needed for Luck, Deadly Strike, Soldier's Luck, and Wide Gates.