Should I look for anything on the walls?

Hint 1 of 11:

One word: Yes.

Hint 2 of 11:

Scattered around are alcoves which contain items which are useful, and
occasionally necessary.

Hint 3 of 11:

Have you seen any odd-colored stones?

Hint 4 of 11:

Have you tried clicking on them?

Hint 5 of 11:

These are secret buttons.  Some of them open doors, others open secret
passages, and still others are linked to puzzles.  You should experiment even
if a button doesn't seem to do anything immediately.

Hint 6 of 11:

There are also runes or writing carved into the walls.

Hint 7 of 11:

Which runes you can understand depends on which races you have in your party.

Hint 8 of 11:

You shouldn't worry too much if you can't understand something, however.  You
don't need to be able to read any of the runes in order to successfully
complete the game.

Hint 9 of 11:

There is one more common thing to look for in walls.