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.