The Philosopher's Stone

The secret to immortality that everyone thought was just a legend...

Though there are many differences between the different people in Aiedrial, one universal thing they all face is death. Everyone must die, as it was decreed by Midas the Sun God in the ancient texts. Death is the continuation of life, the passing on of legacies, and the ultimate adventure. No one has been able to come back from death, so nobody knows what happens beyond it other than The Rider himself. It is a necessary part of the world, and yet it is the most feared thing.
Perhaps it was such fear that led to the discovery of the Philosopher's Stone. A sorcerer named Rowan joined the Healer's Guild with his friend, Arcano, after they graduated from Grimmwood University. When they moved to the royal city in the center of Eland Jandry to investigate an outbreak of The Pox, Rowan focused his studies on a legend he had heard about an alchemist who was able to elongate their lives with the help of a stone. His studies consumed him the deeper he dove into it, and he was able to find a way to craft his own Philosopher's Stone, though the process to make it cost more than he thought it would.
The stone itself is a normal gemstone that has absorbed the aura of a living person, essentially transporting the person's soul out of their body and into the stone. Rowan was not able to find whether or not that process was irreversible, though he and Arcano--the only person he confided his findings to--suspect that it is not, assuring that the person whose aura is moved to the stone is dead, although their soul does not dissipate. 
Anyone who holds the stone and is able to use its magic, whether through study or through ritual, does not become completely immortal, as immortality is not possible outside of the fae realm. Rather, the stone prolongs the aging process of the bearer as long as they hold it. If, however, they lose the stone, the bearer will swiftly age until their physical form catches up to their chronological age. Therefore, if a bearer has been holding the stone for 25 years, they would maintain the appearance of the ae they were when they got it, and if they lost it, their bodies would age 25 years in the span of a few weeks. The longer they had the stone, the longer it will take for their bodies to age.