Demon invasion.

yes, I managed to beat the Necromancer, but it was mostly due to luck. I reloaded the mission until I got a Flesh Tunic guarded by bears, and I took them out in the first turn, leaving me with only one Imp but with 6 spells (artifact + spell boosters + level up). After that, I cleared almost everything without any losses, and by the time I reached the Necropolis, I had 11 spells, but the battle was still very difficult, and I almost lost everyone. I took out his castle, then the Manticore guarding the spell booster and the Phoenixes guarding the Robe of Sar-Issa. I used the rest of my army, and ended up with 18 spells. And in Shi'o, the neutrals are already tough, even with that many spells, it's hard to get through them. How to beat it with reduced spells is a mystery to me.