Inferno vs. Necropolis

A very useful skill for a demon is Inner Flame (or something similar, in the fire skill tree, it adds fire damage to the unit). We give this to the Lords of the Abyss (preferably, develop the Fire magic to the third level – you need a mage hero) and off we go! It’s best to have the other troops take a defensive position (except for the Destroyers and archers) and call in reinforcements. If you have a mage hero, you can cast several more protective spells on the Lords, including healing. For a warrior hero, it’s good to take Counterattack III and Reinforcements III; the latter should also be cast on the Lords (definitely take the fire damage bonus for the warrior!). Personally, I used this strategy to defeat Necropolis in a duel, although it was in the beta.