Descend the stone staircase behind the fourth Dragon Tear into the Crypt of Eternity. At the bottom, enter the hole in the wall and turn left. Arackling Crawlers attack, so enter the hole in melee mode. Follow the passage until it ends in a closed portcullis. You can see the treasure through the portcullis but can't reach it until you complete the Crypt's riddle. A ramp in front of the portcullis descends to the lower level where the riddle begins.
The following riddle is scrawled on the page of an open tome: Sprinkle here, that which remains of two by fire consumed: ash from one who is forever damned, and one who trespassed upon this tomb. You'll need to find two piles of ash to open the treasure vault. Continue to the back of the chamber, where a magical platform awaits. An obelisk lights the gloom in the nearby corner; switch characters if you wish.
When both characters step onto the platform hovering out in the darkness, a purple flame lights up from the disk's base. To move around on the disk, shoot the bells hanging throughout the vast chamber. If you hear a gong, you've successfully struck the bell and the disk will move to that new position.
If you go forward one position and then right one position, you'll reach a long corridor that leads toward your first objective. As you creep down the corridor, though, a giant spider bursts through the wall on your left and attacks. Sprint to try and avoid the spider trap. If the spider grabs you, repeatedly hit the onscreen button to roll free before you receive lethal damage.
Around the next bend, enter the chamber and pick up more gold and a key in the old chest near the chamber's center. As you touch the chest, Skeletons rise from the floor and attack. Shatter them quickly and be on your way.
Return to the starting point and look for the locked door directly behind where the disk docks. The key you found fits this lock and opens the door. Enter and retrieve the heart from the old chest.
Head back out on the disk and go toward the first passage, then turn left and discover the second passage. This leads to a talking door that requires a heart to enter, which you have. The heart opens the sealed door, and you can duck inside to a tall chamber.
A pillar of fire rises ahead. While one character steps on the circular pressure plate near the entrance, the other character can retrieve the first pile of ash from the fire pillar. To complicate matters, though, you'll have to battle through Skeletons the whole time.
Now head over to the third chamber on the bell area's left side. Take the first right in the passage, and beware the pressure plate that triggers a trio of poison darts to fire at your back. Continue down the passage and turn left into the main chamber. Notice the corpse lying on the far side. Approach it and have Caddoc stand on the pressure plate in the chamber's center. The nearby wall brazier ignites and E'lara can light her arrow. Walk over to the corpse and fire a flaming arrow into it. Seconds later, the corpse is reduced to ash, which you can pick up for the second component to the treasure vault riddle. Collect the gold in the room before you leave (careful not to trigger another poison arrow trap behind the treasure chest in the back).
Return to the starting point. You'll hear a growl as you cross the bell area; a Dread has been set loose to destroy anyone who tries to reach the treasure vault. Battle the Dread and then take the two piles of ash back to the tome. The whole pedestal around the tome rises up and connects with the treasure vault you saw earlier through the closed portcullis. Reap the rewards of your hard work: two enchanted weapon racks and two Crystal Chests. With treasures in hand, head back to the room next to the Dragon Tear and enter the door in the corner to continue deeper into the dungeons.