The Philosopher's Stone (Japanese: 賢者の石 Romaji: kenja no ishi, translated as The Stone of Sages in Slayers: Super Explosive Demon Story) is a stone with extremely potent magical properties in the Slayers world. According to legend, the all of the worlds in the Slayers universe are supported by a gigantic staff sticking out of the Sea of Chaos. The stone is reputedly a small broken off piece of that staff. The stone is also later claimed to be a small fragment of the Demon's Blood Talismans. . Because the Talismans are themselves of unknown origin, the explanations are not necessarily mutually exclusive.
The Philosopher's Stone can be used to amplify human magic "a gazillionfold," in the words of Lina Inverse. For example, a regular fireball is about the size of a human head. In the second volume of Slayers: Super Explosive Demon Story, Lina uses the stone to cast a fireball the size of an entire human body. Legend has it that the stone enabled an apprentice sorcerer to destroy an entire kingdom. It is said that every time the stone appears, the course of history changes.
In approximately 1011 AK(?), the stone was unwittingly obtained by Lina Inverse, hidden inside of an Orihalcon goddess statue. Both Rezo the Red Priest and Zelgadiss Graywords tried to steal it from her several times. Rezo wanted the stone to cure his blindness, while Zelgadiss wanted it to get revenge on Rezo for turning him into a chimera. Eventually, Rezo managed to successfully get the stone from Lina through the use of threats. Rezo then used (or rather, ate) the stone in order to summon one of the pieces of Ruby Eye Shabranigdu, hoping that the ma-ō would grant him sight. What Rezo did not expect was that Shabranigdu would be resurrected from within his own body. Rezo-Shabranigdu was destroyed a short time later by Lina Inverse. What happened to the stone after that is unclear. It was most likely destroyed along with Shabranigdu.
The properties of the Philosophers Stone in Slayers are considerably different from its properties in western alchemy legends.