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In my opinion, the author went overboard with the Dungeon. Personally, for me, removing the option described by mvk makes the map virtually impossible to complete. After dealing with the Inferno player (losing "only" the Dark Riders and half of the Furies – I got lucky!), I found a ton of opponents – Dark Elves with legion-sized armies. And all this is in the Light version and on the "Warrior" difficulty level...
The idea of building an army by capturing enemy Castles seems doomed – the opponent's main hero makes excellent use of "Portal," moving to the Castle I'm approaching...
I reached the Dungeon in a "record" time – 10 months, but that was more than enough for the opponent to build up unimaginable armies from 6 (or so?) Castles and – somehow – level up their heroes to a level comparable to my main hero...
I'm not a hardcore player, but I have completed difficult maps before; I know ways to defeat a superior opponent, but not when, for unclear reasons, their initiative is always higher than mine, and my stacks are simply wiped out before I even get a turn...
The author has uploaded replays of their battles in the Dungeon. I dealt with Marbas with fewer losses, but the Dark Elf opponents are significantly tougher...
It's a shame – this is the first map in a relatively long time that has really "hooked" me:(
P.S. However, in the final version, the Elf can be quite easily defeated by Raileigh.