The thirteen auracites (聖石, Seiseki?, lit. Holy Stone) in Final Fantasy Tactics are legendary crystals known as the twelve Holy Stones/Zodiac Stones of the Zodiac Braves of Ivalician legend. The legend of the Zodiac Braves is regarded by the Church of Glabados as the central doctrine of its teachings. The twelve Zodiac Braves are said to have fought the Lucavi demons, driving them back into the spirit world. The legend foretells that the Braves, carrying the Zodiac Stones, would come to save humanity should the world ever be in peril. The Stones themselves are of various colors and shapes.
The legends of your holy auracite are lies! The Stones are magicite—they hold in them power for evil.
In truth, the auracites facilitate the Lucavi's existence in the mortal realm via possession of those who hold their auracite. However, the stones may not be entirely evil, as one helps revive Marach after he is shot while defending his sister. Marach claims to have heard a calm, gentle voice telling him to go back, and speculates the Stones are raw power shaped by the wills of their wielders.
To release the Lucavi, the Stone needs a vessel. It is believed that the host must have the same zodiac sign of the auracite and requires that person to become the Lucavi's vessel, but this is not necessarily true; e.g. Wiegraf Folles is a Virgo, but is possessed by Belias, an Aries. In the case of the Lucavi leader, Ultima, there can only be one vessel for her auracite in so many generations.
Then all that remains is the revival of the master. Once that is done, we will have no need of auracite-nor of these vessels. We will come and go as we please.
The Lucavi seek to revive their master, Ultima, which they believe will release them from the auracite altogether, allowing them passage to the mortal plane as they please. The Lucavi come to possess high ranking Knights Templar and orchestrate a war in Ivalice to facilitate the bloodshed needed for the revival ritual. Ramza Beoulve learns of the truth behind the war and collects the auracites on his travels, but fails to prevent Ultima's revival. Ramza and his friends descend into the nether realm to defeat Ultima right as she is reborn, saving the world.
During his travels Ramza has a chance to see a machine of mysterious powers that reacts to auracites. Construct 8 is an ancient automata discovered by Besrudio Bunansa, and Ramza notices a symbol on the robot, realizing that an auracite (Aquarius Stone) is required to activate it. He recovers the Stone and activates Construct 8. They later find Construct 7, powered by the Cancer Stone.
List of auracites
Capricorn Stone (Goat)
One of the twelve legendary Zodiac Stones. This particular stone bears the symbol of the Goat, and was acquired after defeating Lord Dycedarg in battle.
The Capricorn Stone is obtained by defeating Dycedarg Beoulve possessed by Adrammelech. The Capricorn Stone had been given to him by Loffrey Wodring, one of the Knights Templar, as an "act of goodwill". Dycedarg was unaware of the Stone's supernatural powers, but kept it on his person. When he duels Zalbaag and Ramza and is defeated, the Capricorn Stone takes Dycedarg over, transforming him into the Lucavi demon Adrammelech. Adrammelech wipes out the Northern Sky knights who had been defending him, kills Zalbaag, and attacks Ramza. Ramza prevails, kills Adrammelech, and recovers the auracite.
Aquarius Stone (Water Bearer)
One of the twelve legendary Zodiac Stones. This particular stone bears the symbol of the Water Bearer, and was recovered from the depths of a Gollund coal mine.
The auracite is with Beowulf Cadmus. Grateful to Ramza's help, Beowulf rewards him with the auracite when he joins Ramza's roster of allies for good. Aquarius is an optional auracite for the player to obtain, as Beowulf is a secret character. Ramza takes the stone back to the Clockwork City of Goug where he uses it to activate Construct 8, an ancient automata.
Pisces Stone (Fish)
One of the twelve legendary Zodiac Stones. This particular stone bears the symbol of the Fish, and was entrusted to Alma by Ser Isilud just before his death.
The Pisces Stone is obtained from Isilud after his death. Isilud joined the Knights Templar with his father, Folmarv Tengille, and was entrusted with the Pisces Stone. After learning of the truth of the Stones and the Lucavi, Isilud tries to stop his father who is now possessed by Hashmal, but is defeated. Alma Beoulve tries to help him, and Isilud hands her the Pisces Stone asking her to pass on his forgiveness to Ramza. The Virgo Stone also in Isilud's possession reacts to Alma, prompting Folmarv to kidnap her. Alma drops the Pisces Stone during the scuffle and Ramza finds it when he arrives at the scene.
Aries Stone (Ram)
One of the twelve legendary Zodiac Stones. This particular stone bears the symbol of the Ram, and was obtained after defeating Wiegraf Folles in battle.
Aries Stone is obtained by defeating Wiegraf possessed by Belias. The leader of the templars, Folmarv Tengille, gave Wiegraf the Aries Stone, presumably as a goodwill gift, but with the actual intention of making him the host of Belias. Later on, when Wiegraf attempts to avenge his sister's death, he loses to Ramza and the Aries Stone activates. Wiegraf hears a voice telling him to commit his soul to the Stone.
God Stone bearer, with me now do treat. Your spirit and my flesh as one shall merge. Life undying yours forever more. Your ire and despair, their call I heed. And so once more I ask: With me do tread. The Gigas Belias have I been named. Your plea to answer now my only wish.The Stone speaking to Wiegraf
Despite Ramza's objections, Wiegraf commits and transforms into Belias, teleporting away. When the two next meet Ramza claims Milleuda would never have wanted her brother to become the monster he is. Wiegraf explains he no longer fights to gain revenge for Milleuda, and his sole goal is to bring chaos to the world. Wiegraf transforms into Belias and summons three Archaeodaemons to even the scales, but Ramza still prevails. Belias explodes and the Aries Stone drops harmlessly to the ground.
Taurus Stone (Bull)
One of the twelve legendary Zodiac Stones. This particular stone bears the symbol of the Bull, and was discovered deep beneath the Clockwork City of Goug.
The Taurus Stone is obtained with Mustadio Bunansa. Mustadio and his father, Besrudio, came into possession of the Taurus Stone, the latter having discovered it at an excavating site in the Clockwork City of Goug. Cardinal Alphonse Delacroix seeks the Stone and hired Ludovich Baert, leader of Baert Trading Company, to obtain it by force. Baert's minions captured Besrudio, but Mustadio escaped and joins Ramza.
Baert threatens to kill Besrudio if Mustadio does not divulge the location of the Taurus Stone. Mustadio claims it is in a chimney and Baert has Ramza retrieve it for him before he leaves. Besrudio bemoans the loss of the Stone, but Mustadio reveals the one in Baert's hands is a fake, and that he has the real Taurus Stone.
Gemini Stone (Twins)
One of the twelve legendary Zodiac Stones. This particular stone bears the symbol of the Twins, and was acquired after defeating the marquis Elmdore de Limberry.
The Gemini Stone is obtained by defeating Marquis Elmdore possessed by Zalera. When the War of the Lions breaks out, Elmdore fights on the side of the Order of the Southern Sky. He is mortally wounded, but because he was holding the Gemini Stone, he does not die, but becomes a host to Zalera and begins working with the other Lucavi to revive Ultima. After Ramza kills Zalera, he recovers the Gemini Stone.
Cancer Stone (Crab)
One of the twelve legendary Zodiac Stones. This particular stone bears the symbol of the Crab, and was acquired after defeating Construct 7.
The Cancer Stone is obtained by defeating Construct 7. Construct 7 is a robot from the days of Saint Ajora Glabados who guards the Nelveska Temple. After Ramza's party defeats it, Construct 7 drops the Cancer Stone. The party uses it to restore Reis Duelar to her human form. Doing the sidequest and thus obtaining the Cancer Stone is optional. Taking the Cancer Stone to Besrudio, they activate an inter-dimensional portal with it and summon Cloud Strife.
Leo Stone (Lion)
One of the twelve legendary Zodiac Stones. This particular stone bears the symbol of the Lion, and was acquired after defeating Lord Folmarv of the Knights Templar.
The Leo Stone is obtained by defeating the second Lucavi in command, Hashmal, who had it in his possession. Because Leo is obtained past the point of no return, though it has an artefact menu entry, it cannot be viewed in a normal playthrough as the player cannot enter the menu.
Virgo Stone (Maiden)
One of the twelve legendary Zodiac Stones. This particular stone bears the symbol of the Maiden, and was acquired after defeating Ultima, the High Seraph.
The Virgo Stone is obtained by defeating the leader of the Lucavi, Ultima. Because it is obtained past the point of no return, though it has an artefact menu entry, it cannot be viewed in a normal playthrough as the player cannot enter the menu.
The Stone was kept in the Orbonne Monastery where Alma Beoulve saw it and told Ramza about it. Seeking to prevent Ultima's resurrection and to get his hands on the Stone before the Knights Templar, Ramza and Alma and their friends head to the monastery but are too late. The Knights Templar abscond with the Stone, and in the process learn that Virgo reacts to Alma, marking her as a suitable host for Ultima. Folmarv, the leader of the Knights Templar, takes Alma to the Airship Graveyard to perform the resurrection ritual and ends up using his own life as a sacrifice to complete it. Ramza follows to rescue his sister, and defeats Ultima right as she is reborn, claiming the Virgo Stone.
Libra Stone (Scales)
One of the twelve legendary Zodiac Stones. This particular stone bears the symbol of the Scales, and was a valued heirloom of House Orlandeau.
The Libra Stone is obtained with Cidolfus Orlandeau, who brings it along when he joins Ramza, the Stone having been an heirloom in his clan.
Scorpio Stone (Scorpion)
One of the twelve legendary Zodiac Stones. This particular stone bears the symbol of the Scorpion, and was acquired after defeating Cardinal Delacroix in battle.
The Scorpio Stone is obtained by defeating Cardinal Delacroix possessed by Cúchulainn. When the cardinal greets Mustadio, Ramza, Agrias and Ovelia, who seek the protection of the church, he reveals he has the Scorpio Stone. He tells Mustadio about the Zodiac Brave Legend and agrees to shelter Ovelia. Agrias remains with Ovelia, while Ramza and Mustadio depart for the Clockwork City of Goug to save Mustadio's father. Delacroix has Ovelia imprisoned, but Agrias escapes. When they next meet, Delacroix transforms into Cúchulainn and attacks Ramza and company, but is killed, leaving the Scorpio Stone behind for Ramza to grab.
Ramza is branded a heretic with the accusation that he had killed the cardinal and stolen the auracite. Later on, when Ramza's friend Rapha Galthena's brother Marach is killed in batter she mourns the loss and the Scorpio Stone reacts. Rather than turning Marach into a Lucavi, it revives him.
Sagittarius Stone (Archer)
One of the twelve legendary Zodiac Stones. This particular stone bears the symbol of the Archer, and was entrusted to Meliadoul of the Knights Templar by the High Confessor.
The Sagittarius Stone is obtained with Meliadoul Tengille, who defects the Knights Templar to join Ramza.
A thirteenth Zodiac Stone, newly added to the Zodiac. It is gained once Elidibus is defeated.
The Aries stone is an accessory, and was attainable by defeating Belias in a Final Fantasy Tactics event. When equipped, the stone provides a +30 bonus to the wielder's Attack stat. The Aeries has Synergy with the Final Fantasy Tactics realm.