The Mage Stone is a magical stone wielded by the renegade sorcererTauren. It appears to be made out of Baltic amber and is held in metal shaped into a claw. This is an ancient and powerful magical tool capable of transmutation, which is to change the very essence of things. The spell that Tauren used to turn lead into gold was: "Ferian æt gylden. Ic búgan þéos. Ferian æt gylden" (which means: "It changes to golden. I submit this. It changes to golden").
The Mage Stone is also capable of absorbing and deflecting magical blasts of energy. When someone with magical powers holds the Stone, it resonates and the strong magic that emanates can be felt from far away. For centuries alchemists have attempted to use various methods to change essences, particularly base metals into gold. However no one has been successful, Tauren is seen to be using the magic of the Mage Stone fulfilling part of the alchemists' great work. Tauren was killed by Morgana. He kept the stone in a small pouch at his belt. What happened to it after his death is unknown, although it is safe to assume that it is held in Camelot's vaults, like other forbidden magical objects (To Kill the King).
The Mage Stone is based on "The Philosopher's Stone", the legendary object that is said to be able to transmute any metal into gold or silver, produce the Elixir of Life and create a Panacea. The Stone was considered the "Holy Grail" of Alchemy and was long sought by Alchemists.