Walkthroughs for custom maps.

Who says that? Or are you referring to a bug where creatures don't move at all?

I did some digging through forum reviews while looking for good maps for the old Heroes 3. It seems to refer to a massive burst of damage in an area, as it makes the game too easy.

Added 1 minute ago

If I'm not mistaken, I didn't spend mana there, but used the Boots of Levitation.

Mana isn't a big deal. I climbed onto the boat to see the maximum on this island and the next 2-3 free spaces after the griffins.