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I once left that location with 19 Warmongers and 51 Trappers, taking everything except the hut with useless shamanism. Luckily, I had enough troops to continue.
Nevertheless, I'll still have to find the Grail randomly. I took all the obelisks, except for the bugged one at 8-5, which is inaccessible, and the map isn't revealed. There are also bugged Knowledge Crystals that can't be collected, in the first mission near the Druids, and in the second at 47-61.
There are crystals that don't light up; they are replaced with red ones from the Demon location, meaning something like a demon or a stone.
Added 14 hours 28 minutes ago
In the third mission, there's a thing: if you retake an Orcish town, the buildings in it will still be destroyed. In principle, this could be useful for re-acquiring spells. For example, I don't have "Wrath of the Horde" and "Word of the Leader" from the two starting towns.
Yes, because it would be too difficult to attack 6 Companions with an army from 5 or even 4 castles.
Added 49 minutes ago
And there's another thing in the third mission: I managed to gather a decent army, but the Companions keep running away. It's easier to play this way, but in some other maps, there were some restrictions that prevented the AI from running away; that would be helpful. I do have manacles, but since I've reached the experience limit, it doesn't matter if they run away or fight – I just want to occasionally grab artifacts. I won't specifically use manacles, firstly because luck will drop from 2 to 0, and secondly, I'll have more losses, and why would I want that if I've already reached the experience limit?