Nevertheless, I 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 Crystals of Knowledge that can't be collected, in the first mission near the Druids, and in the second mission at 47-61.
Added after 14 hours 28 minutes
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 can be useful for re-acquiring spells, for example, I don't have "Wrath of the Horde" and "Word of the Chieftain" from the two starting towns.
Added after 49 minutes
And there's another thing in the third mission: I manage to build up a decent army, but the computer-controlled armies constantly run away. This makes the game easier, of course, but in some other maps, there were some restrictions that prevented the computer from running away; that would be helpful. I do have Shackles, but since I've reached the experience limit, it doesn't matter whether they run away or fight – I might occasionally grab some artifacts. I won't go out of my way to use Shackles, firstly because my 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?