In order to complete this quest you need to you need to look for three clues to open the stone tablet, the location for the three clues located nearby the Ruin Tablet shows in Step 1, from the screenshot :
1. You need to break the Ore nearby, after you have break you will receive a fragment lead it to the lantern, total got 2 shows in Step 2 and 3. For 2 and 3 defeat all the enemy around if require shows in Step 4 and 5 respectively.

After you have break all the three seal break, bring the light cube back to the Ruin Tablet quest completed shows in Step 6, inside the Ruin having three Precious Chest.