Inferno tactics.

What rules are you playing by? If diplomacy is allowed, take a diplomat hero, build up your town, gather resources, and recruit monsters. And in general, agree on the rules before the game so that the Necropolis doesn't build the Necromancy Amplifier, otherwise it becomes overpowered... And remember that Efreet + Armageddon is also a good strategy. (But overall, it's a suicidal strategy.)