[danko]

A slight spoiler, but there's a reason why some spaces are '?' - they hint that one specific type of creature may be nearby. (Think of the one that looks like a Beholder from D&D).

For the walls - think of them as an HP sink. The game largely revolves around using your health as efficiently as possible to explore the board. Walls are useful since you can attack them 1 HP at a time to get the XP out of them (thus allowing you to always fully use your allotment before refilling your health).