It is recommended to have at least level 5 or 6 before doing this puzzle.
This puzzle is located in a northern part of the Cyseal map. Exit the city through the northern gate and follow west until you reach a fork in a road. Now follow north until you can see a sick-looking dog, a hatch and several stones.
If you click on a dog or try to open a nearby chest a fight with several undead will ensue.
It is recommended to clear enemies at this location first.
Move north until you notice a circle of fire, several Lesser Infernal Chimera and an Undead Pyromancer. Use rain and clear this location as well. Notice another chest and a hatch nearby.
Unchain one or two (in case you got 3 or 4) characters and move them back to the first hatch.
Now enter through the first hatch. Notice an iron ore node to left.
Inside you will find 4 columns corresponding to 4 elements and a tombstone with hints relating to the puzzle on it.
Click on the switches below the columns in this order:
Now switch to the other characters and enter a second hatch. You should see a Mysterious Opponent spawned inside which looks like one of your main characters. Kill it and loot the Round Pendant. Notice another iron ore node and yet another hatch.
Now click on the switches below the columns in this room in this order:
Switch to your other characters and kill another mysterious opponent. Loot the Square Pendant.
Using both of your character teams enter two new hatches and move through the caves until you notice two forcefields blocking your way. Open you inventory and drag-and-drop one of the pendants on a nearby pedestal. Repeat on a second character.
Now that forcefields have been lifted you can loot 4 Ornate chests inside and chain back your characters.