"A treasure sought by medieval alchemists, who believed they could change base metals into gold."
This mystical stone is located in the Cavern of the Gods, in front of the statue in the Altar of Osiris. It is a one-time salvage item found using the clues in the treasure rumor called "Okeanos Tablet 2" in the player's notebook. In order for this treasure rumor to be activated, the player must have found the Cavern of the Gods. This means that they can find it before the end of the main plot as long as they return to Nineball Island before they search for it.