The Stone Key Ruins are one of many ancient structures scattered around the New Cyana Islands. This particular structure has been difficult to find due to the ruins being very small compared to the others.
The ruins can be found on the south shore of the "bay" in the center of the Sapphire Islands, on a piece of land that points inwards. The Key has no function until a puzzle is solved to unlock it. To solve the puzzle, the player must click several stars in the sky. While these starts are just barely visable during the day, they shine just a bit brighter than the other stars during the night. When the stars are clicked, they will glow brighter as an indication. When all stars are glowing, the circular platform below the key will levitate and face the player. This will open a portal to Vaultus. There are nine stars, with five on the left and four on the right.