This quest is the last in the line that begun with 'A Life’s Dedication'. The last stele can be found in the Burned Temple of Charites at Orchomenos City, located on the north western shores of Lake Kopais. When you reach the temple, interact with the search icons associated with specific items in and around the ruins. You should also speak with the woman who is waiting at the temple, who will provide you will valuable information about the location of the people who burnt the temple. When you have investigated all of the clothes, use Ikaros to identify the culprit and make your way south west to find and kill him. The man will be dressed in the clothes of a citizen, and will attack you if he notices your approach. Kill him instantly with an arrow to the head. You can then loot the body for the stele piece, which will complete this part of the quest.
Keep the Faith
Now that you have the last piece of the stele, return to Eppie in the Cave of the Oracle to discern the last piece of the puzzle. A cut scene will initiate when you speak with him, and you will have the option to lie or be honest about what you are seeing. Either way, there will be no great difference to the end of the quest, other than the reaction of Eppie. When you are done speaking with him, you will acquire all pieces of the ancient armour and the quest will complete.