when you approach the Warmongers near the Necropolis, the only city is reset to level 1. This happens every time you step on a specific tile (and not just one, but several), meaning it happens repeatedly. You're bound to step on one of these tiles if you want to reach the castle – so how are you supposed to defeat the Barbarians when resources are limited and there's nowhere to go? As a result, you can't build much on your hero, and you simply don't have the means to defeat strong neutral creatures – and with this setup, if you don't get lucky with item drops, you can't progress. Also, the Mentor is invisible, and the Summoning magic is completely useless, as it just blocks the tile, although at least I got a spellbook. Never mind the Mentor if it weren't for the useless spell blocking the tile... (and even if it did, at least it could give improved troops, but that's secondary; resetting the city is a critical bug). By the way, only the first city was reset for me; in principle, it's a fair 1:1 match against the Necropolis, if you don't reset it, of course.
Added after 20 hours and 15 minutes
in general, if you fix at least the city reset when stepping on tiles near the Warmongers at the Necropolis, it would be a pretty good map for a short playthrough; this city reset is a major drawback.