Runelocked Chest

So, there is another one of these quests with the same name but 31 Yellow Runes to destroy - I was not able to find that quest on Wowhead but I think they're all fundamentally the same.

The strategy is to click 2 runes adjacent to each other resulting in 3 runes to be lined up in a row, either horizontally or vertically, like Tic-Tac-Toe.
When 3 of the same runes line up in a row, they disappear and the runes above them drop into their place. Line up the yellow runes 3 in a row enough times to destroy the yellow runes, and voila!

You can only swap runes that are next to each other (above, below, to the right or left of the rune), and only when that swap causes 3 runes to be in a row.

At first, or maybe even after several minutes, it might seem insoluble; it requires some patience; look for patterns.

Turn west off the path at 60, 23 and enter the mini-palace. You will find the game on the balcony to the south. If you go all the way to the lower levels and jump in the water you will end up finding a pet battle: Frenzied Knifefang.

There are 18 Runelocked Chest World Quests.

Easy Runelocked Chest: Yellow
Easy Runelocked Chest: Red
Easy Runelocked Chest: Purple
Easy Runelocked Chest: Orange
Easy Runelocked Chest: Green
Easy Runelocked Chest: Blue

Medium Runelocked Chest: Yellow
Medium Runelocked Chest: Red
Medium Runelocked Chest: Purple
Medium Runelocked Chest: Orange
Medium Runelocked Chest: Green
Medium Runelocked Chest: Blue

Hard Runelocked Chest: Yellow
Hard Runelocked Chest: Red
Hard Runelocked Chest: Purple
Hard Runelocked Chest: Orange
Hard Runelocked Chest: Green
Hard Runelocked Chest: Blue

These are part of the achievement "Puzzle Performer"

To unlock these World Quests you have to first find a Silver Knife
which can be found in any of the arcane chests in Nazjatar

This puzzle game is optional, so if you don't like it, don't play it.
I personally like these quests. It gives me a break from killing.

The mechanics work like this:

The game consists of a 8 x 8 grid which is composed of 6 different colored runes.

1] Click on any rune.

2] Click on any adjacent rune and those two runes will swap positions.

3] If, by swapping those two runes, you cause 3 runes in a row to all be of the same color, then those three runes will be destroyed.

4] If, by swapping those two runes, you do not cause 3 runes in a row to all be of the same color, then those two runes will swap back to the positions they were in and nothing happens.

5] An adjacent rune is considered to be to the left, right, up, or down.

6] A row can be left to right or up and down.

7] When runes are destroyed, each rune (and all the runes in that column above that rune) will fall downward.

8] If you cause more than 3 runes to be in the same row or column, then all of the runes of that color will be destroyed. So, for example, if you cause 4 runes to be the same color, all 4 of those runes will be destroyed.

9] If you get stuck, you can exit the game and restart it.
I personally have never gotten stuck, but one time for me the quest completed before I reached the goal. Apparently, that time, randomness left the puzzle unsolvable.

10] To exit the game, click on the Arcane buff in the upper right of your screen.

The object of the game is to destroy a fixed number of runes of one particular color, but you can destroy as many runes of any color to keep changing the pattern of the grid.