The most important units in the Necropolis are vampires, liches, death knights, and skeleton archers (if there is a good necromancer).
In battle, owns Necromancers do not lose troops, but gain them, unlike Sylvan Elves (who find it difficult to replenish losses). It makes no difference to them which town they capture; everyone will be turned into skeletons. At high levels, Necromancers cast powerful weakening magic, and knowing Berserk or Hypnosis... only a Warlock has better SpellPower. If Logistics is developed, a Necromancer can amass huge armies in just a few weeks of game time.