From ZAM:
The puzzle is located at (3140, 4420) in Scarwood Reach.
To solve the puzzle, approach the row of pillars. Stand facing the pillars that have 6 red crystals on them, three on the left and three on the right.
LEFT RIGHT
1 2
3 4
5 6
Press 4-5 in any sequence. You will get a key that opens a chest that pops nearby.
Note: The puzzle can be solved at any level, but the "A Dusty Sack" loot has a required level of 40.
In case it doesn't work, find the numbers of the current state of the puzzle. I mean which torches are missing by using this picture. In the picture, it is 7, 4, 13 (the default state). Then look at the table below to find the number of times you have to click on each button (the order does not matter).
If you made a mistake while typing the combination (1 4 5 2) reset the situation by hopping to another shard and carefully re-entering the tight combination.