This puzzle can be accessed by going to (4539, 2380) at Shadefallen Keep in the northwest part of Gloamwood. The main castle at the back has a plaque on the west wall (View video guide to see where the plaque is). Click on the Mysterious Plaque to be teleported to the tower with the puzzle.
There is a helpful application at RiftIdeas.com. Tell it what the order of the shields is and it will tell you how to rearrange them into the correct order!
The rewards for this puzzle start at level 20 and max out at level 35.