The Stone-Sheathed Sword is one of the most interesting items added in Elden Ring: Shadow of the Erdtree. You can transform it into two powerful new weapons, the Sword of Light or the Sword of Darkness, and there are a few quirks in the system that you should know about.
Location of the Elden Ring DLC sword with stone sheath
You can pick up the Stone-Sheathed Sword in three places in Elden Ring: Shadow of the Erdtree. Three altars are hidden throughout the Land of Shadow, and the first one you interact with will give you the Stone-Sheathed Sword. The other two altars will be places to transform the Stone-Sheathed Sword into either the Sword of Light or the Sword of Darkness.
One of the three altars is a lot harder to reach, so you'll need to pick up the Stone-Sheathed Sword from this altar first.
The most inconvenient altar to reach is also the one closest to the start of Shadow of the Erdtree. You can reach Fog Rift Catacombs immediately after starting the expansion. Cross Ellac Greatbridge until you’re outside Castle Ensis, then turn left and head downhill through the valley. You’ll emerge in a grassy lowland area, and the entrance to Fog Rift Catacombs is around the back.