The Philosopher's Stone (賢者の石, Kenja no Ishi), also known by various other names such as the Red Stone, the Fifth Element, also the Senguin Star in surrounding countries and the Grand Elixir in its liquid form and many more, is a powerful transmutation amplifier surrounded by conjecture and mythos. Due to the absolute law of alchemy being equivalent exchange, the stone gives the illusion that someone is able to override that law. Being that it is an illusion, the powers of the stone itself are not unlimited, and only appears to allow an alchemist to bypass equivalent exchange as long as the stone retains its power. It is also to be noted that the philosopher's stone only amplifies the abilities of an alchemist according to their skills and ability. This being the case it may not always work while bringing a human back to life. If a solid body isn't present it will not work and sacrifices will be made to substitute.
Comprised entirely of human souls, Philosopher's Stones are rare and seen by the vast majority as the ultimate moral taboo to create, at least, those who know what they are actually made of. The only way for one to truly know their components would be to have had access to one, seen one created, or been told in some fashion by someone who already knew. It is NOT common knowledge and most people that have even HEARD of them pass them off as legends.
HISTORY
The first stone in history was transmuted by the original homunculus later known as "Father", using the souls of the people of Xerxes. This event inspired the legend of a country which was destroyed in a single night. The later Philosopher's Stones were transmuted by the Amestrian government and their State alchemists who were instructed to make the Stones by Father's original Homunculi, using the lives of Ishvalan prisoners, and later the makers themselves to cover it up. These were the first stones created by anyone other than father- they were made from only about 13 prisoners
Generally believed to exist only in legend, the Philosopher's Stone has long been sought by alchemists as the ultimate goal of their craft. While alchemy is an amazing preternatural art in and of itself, its scientific limitations are such that the dream of a mystical and mythical object capable of eradicating those limits is one shared by generations of practitioners. Though, in more pragmatic times, the legend of the Philosopher's Stone has come to exist only in the fanciful illusions of Romantics, the fabled amplifier is, in fact, an arcane reality.
CREATION
The stones are created using a specialized transmutation circle that can only be learned by visiting the ruins of Xerxes, and doing research for three topics, at the cost of 2,000,000 cenz. OR having been made to use the circle by the Amestrian government who managed to find the formula another way during the beginning of the Ishvallan Conflict. To create a stone, one must place at LEAST five sacrifices around the edges of the transmutation circle, where their souls will be drawn out and forged into a sphere. Homunculi and Pseudo-Homunculi are the only known creatures/beings known to naturally possess a stone, though it is not exactly common in the case of Pseudo-Homunculi.
ABILITIES
One who possesses a stone will gain the ability to use alchemy without even the need for a clap, much less a circle. This alchemy can be preformed with little effort, even circumventing equivalent exchange to a degree, though you must create from something, as you cannot create something from nothing, even with a stone.
It also increases ones proficiency with Alchemy, increasing ones skill by one full level. Meaning, a beginner becomes intermediate, and advanced becomes a master, and even someone with no skill will gain the ability to use beginner level alchemy provided they have the knowledge.
As long as a stone has at least a single soul remaining in it, it will function to its fullest degree. Souls are cost only by the owner of the stone dying. For each time they die, a soul is automatically expended to bring them back. The only way to attain new souls/more souls, is to kill humans. Chimera/Homunculi do not count towards this. One can also eat other stones to gain all of the souls they have into ones own stone.