When you examine the portrait with the magnifying glass, you see the letters "FMLTRLTM" and it mentions an upside down left hand.

The five buttons correspond to each digit of the left hand when turned upside down. Going from left to right, you have your little finger (L), ring finger (R), middle finger (M), forefinger (F), and thumb (T). So imagine the five buttons as L, R, M, F, T. (1, 2, 3, 4, 5)


With this in mind, the puzzle is solved by pressing the buttons in this order 4-3-1-5-2-1-5-3.

After you look at the Rune Book, you'll see that the runes represent the letters E, H, N, M, R, P, X, O.


Once you look at the pillar near the lake, you see that it has the same runes etched into buttons on it. Usually, when you hit a bunch of buttons in sequence, you expect something to move, open, or change. Looking at the letters we have, the only thing we can spell is OPEN. Pressing the runes that look like a wavy F, a crooked C, an M and a lower case T will give you the desired results.

If you're like me and get stuck on a puzzle, it is nice to have someone give you the correct answer, but I always want to know HOW they came to this conclusion (which isn't always explained in a walkthrough).