World Championship in Heroes of Might and Magic III.

I wrote it this way precisely because I've encountered similar situations in my maps multiple times. Even in "Leto" games, this kind of generation occurs. For example, near a Castle, I've seen an Angel Enclave guarded by a horde of Mummies – I took it on the first turn. Also, ranged units can easily break through Griffins, Demons, and Pit Fiends (though the Swamp might have a harder time with that), up to 10 creatures of level 6, and sometimes even 10+ Manticores, Vivs, and Nags, etc. For Necropolis, I took a Consul level 3 on day 116 (see screenshot). I'm actually happy about your optimism, because I was starting to think that the Swamp is significantly weaker than the Castle on 8mm, or maybe I've just been having bad luck with the map generation.