Great Crystal (Crystal Chronicles)

The Great Crystal is, as its name suggests, a very large crystal, and one of the focal points of the plot of the Final Fantasy Crystal Chronicles series. It has the power of altering the fates of every single person in the world.

Final Fantasy Crystal Chronicles: Ring of Fates
In Ring of Fates, the Great Crystal is kept within a cavern beneath the city of Rebena Te Ra, during a time that, at the time of Crystal Chronicles, would be known as the Golden Age. The citizens often go to pray in front of the Great Crystal kept within the Crystal Temple. Starsingers are people that wield the power of the Great Crystal.

The Latin phrase Ibi in Crystallum inscibuntur omnia fata that appears on the the artwork depicting the protagonists of Ring of Fates is a straightforward description of the power crystal: it means literally "There in the Crystal all fates are written".

Final Fantasy Crystal Chronicles
In Crystal Chronicles, the Great Crystal is no longer in one piece. At some point between the end of Ring of Fates and the start of Crystal Chronicles, a meteor, containing the Meteor Parasite, fell from the sky and shattered the Great Crystal. The meteor then began emitting miasma, which began to spread throughout the world. Those that survived soon discovered that the shards of the Great Crystal kept the miasma at bay and then built their new settlements around the scattered shards of the Great Crystal, which were the only thing that could protect them. The effect did not last and myrrh was needed to replenish the protective effect with. Thus began what became known as the Crystal Cycle.

Final Fantasy Crystal Chronicles: My Life as a King
In My Life as a King, a piece of the Great Crystal appears within the center of Padarak. It grants King Leo the power of "Architek" to rebuild his Kingdom that was destroyed during the time when Miasma covered the world. It is later discovered that the former ruler of Padarak, the Dark Lord, heart resides within the crystal after his body had been destroyed once the Miasma cleared. When he appears before King Leo, the crystal glows an eerie dark purple. After enough Elementites is collected to restore his body, the Dark Lord leaves the crystal and over time it start to glow brighter as the Kingdom grows larger. It is never made clear if it was the crystal speaking to Leo or the Dark Lord trapped within it. Its motives are also unclear as it had originally granted the Dark Lord the power of Architek, although this could have been before the miasma had turned the Dark Lord into a monster as it is said that he was once human.