This quest follows directly on from 'Language of the Ancients'. In order to uncover another piece of the stele text, you must reach the Tomb of Orion, which is located south east of Thebes. When you enter the romb a brief cut scene will initiate in which a man warns you about his companions who have gone insane after they discovered an artefact. When he dies, you will be able to enter and explore the cave, looting as you go. As you wander through the rooms you will encounter a number of snakes. The most effective way of dealing with them is by striking with your torch. This should kill them instantly in one hit. You should also be cautious of the spike traps which rise from the platforms in the ground. Perform a dodge roll if you activate them to avoid the damage. Head east within the tomb and you will encounter a room with a stele statue inside it. Interact with the statue to earn an ability point and some XP. You can now turn west and loot the treasure chests contained within the room opposite. Now head north until you discover a room with a treasure chest in the centre. Loot it and then move the storage containers to exit the tomb.
When you are out of the tomb, head south east to where the crazed worshippers are located atop a hill in the Oropos Heights. As you approach the hill, use Ikaros to identify their precise location in the Cave of Madness. Equip your torch and venture inside. There will be no reasoning with them, so you must kill them immediately. Take advantage of your ambush by assassinating the nearest one to the entrance. When all are dead you can loot the bodies to recover the stele. Be sure to loot the cave of its treasure and ore contents before you leave. With the stele piece in hand, return to Eppie in the Cave of the Oracle to complete the quest. You can now move on to 'Origins of a Ritual' to find the last stele and complete the quest chain.