Tactics for playing against a Necromancer.

I would like to get some help with playing against a Necromancer on the map "Former Friends". Difficulty level: Hero. The opponent is Kaspar. He moves to the center at the beginning of the second week, clearing out the neutral creatures without any losses. So far, I've only managed to win with the Dark Elves – because I can easily go into the dungeon and clear out the neutral creatures at the same speed. With Dwarves, Orcs, Knights, or Elves, I am practically helpless against him, especially if I have unfavorable stacks of neutral creatures (Elven Archers at the entrance to the dungeon and near the gold mine). Either he has hordes of Fire Elementals and a Phoenix, or he uses control spells or the "Unholy Word" spell, which kills my "army" in the second or third week with just a few casts.