Walkthroughs for custom maps.

I mean the battlefields where there is a closed cell.
The idea of many "complex" maps is to "find a loophole" and hide a stack in it.

That's exactly it. In many battles, it comes down to hiding a unit in a safe zone. Either on a plain or in a castle, somehow block one stack, cast hypnosis, and hide your main stack between this unit and a conditional tent. And then you have to figure out what spell to cast so that the computer doesn't cast a spell to remove the charm or antimagic, or so that some archer doesn't finish us off).
But this is much more fun and challenging than in many simpler maps where it's just wall against wall, clone against archons, and then we resurrect.