Taking of the Necropolis [COMPLETE EDITION]

The person who came up with this deserves a Nobel Prize. It's brilliant and simple!

Perhaps, to avoid violating copyright, I'll list the authors of these strategies. Huge thanks to nub_hmm for his amazing tactics for Castle and Tower. He also streams, here's his Justin.tv channel: http://ru.justin.tv/nub_hmm/videos We came up with the tactic for Swamp together, gradually improving each other's strategies. The tactics for Rampart, Necropolis, and Dungeon belong to the Chinese. I came up with the tactic for Conflux myself. This is what amazing results the spirit of competition can lead to!

Why do Necromancers attack the single unit at the bottom instead of the main stack?

Which battle are you referring to?