The Zodiac Stones appear and heard throwout the whole game of Final Fantasy Tactics. The auracite in this game does not help in summoning Espers. Instead, they hold the spirits of Lucavi, some of which appear as Espers in Final Fantasy XII and are the new name of the twelve Holy Stones/Zodiac Stones of the Zodiac Braves and are crystals of auracite instead of Holy Stones.
The Auracites are artefacts, and there are a total of thirteen. Twelve are associated with signs of the Zodiac, while the thirteenth is associated with Serpentarius.
The Zodiac Stones are a prominent element in the story of the Zodiac Brave Story, a legend highly regarded by the Church of Glabados as the central doctrine of the religion's teachings. The twelve Zodiac Braves, in legend, fought against the Lucavi, driving them back into the spirit world. The legend goes on to say that the Braves, carrying the Zodiac Stones in hand, would come to save humanity should they ever be in peril.
They may not be entirely evil, as one helped revive Malak Galthana after he was shot while defending his sister. Malak claimed to have heard a calm, gentle voice telling him to go back. Ramza has said that perhaps it was God to tell him to go back, and that the will of its wielder shapes it. To release the Lucavi seal in the auracite, the stone needs a vessel. It is believed that this host must have the same Zodiac sign of the auracite that the vessel holds and requires that person to become the Lucavi's vessel, but this is not necessarily true, especially with the case of Wiegraf Folles (who is a Virgo, but is possessed by Belias, an Aries). In the case of the Lucavi leader, Alitma, there can only be one vessel for her auracite in so many generations.
It is said that the zodiac Signs might be really the Chinese zodiac.