Walkthroughs for custom maps.

Could you provide a more detailed description of the walkthrough, perhaps with screenshots or save files?

I find this Necromancer behavior rather strange, as I frequently encounter Necromancers emerging from single-player maps in various locations, and they start taking over everything instead of just occupying neutral towns.

1. There aren't really any more details than those described above. The main point is that only two Necromancers crawled to the lower (non-Necromancer) half of the map – the one I mentioned. And the one that jumps into the teleport and then sits in the corner, behind the green gate. That's it! I crushed the rest of the Necromancers near the blue tent (there were 3 of them huddled together). And I did it on their territory, and they just sat around in their castles. Unlike the pink one (I think it was pink), who managed to reach the Necromancer's territory and captured several cities – that pink one really made things difficult.
I don't have any save files or screenshots – I don't have that habit; I usually delete everything after completing a map – why keep it? Plus, I was also annoyed by the map creator – the ending is completely uninteresting – in addition to the Earth and Air skill books, they give you 4,000 Archons for free, which turns the final battle with Kharas into a walk in the park. So, I deleted all the saves without regret – the map didn't live up to my expectations.

2. Maybe this is the author's gimmick: that at a certain phase of the moon and star alignment, the Necromancer starts acting strangely? And you just have to catch that moment.
Otherwise, the map seems completely impossible to beat. The Necromancer's advantage in army and stats is unreal.