Template:Sideicon A Soul Crystal is a piece of equipment in Final Fantasy XIV that changes the character into the job related to the Soul Crystal. Changing into a job enables new abilities and paves the way for the rest of the character's progression along their class. Formerly, it limited the amount of role actions a player could use from ten to five, but later Stormblood patches allow all actions to be used as a stop-gap for a future cross-class skill system.
What a Soul Crystal actually is is largely unexplored, but its stated purpose varies from job to job and it is consistently described as having a wealth of knowledge related to the job contained within it, containing an extreme concentration of aether, and being carved with the deeds and exploits of past people to hold the job's mantle. The exception to the lattermost rule is Machinist, a job new to the world of Final Fantasy XIV with a Soul Crystal described as pristine as a result. Machinist also reveals that Soul Crystals are manufactured, or can be manufactured.
Generally a magic-related job attributes some importance of the crystal to their actual spellcasting, such as the crystal for Black Mage being necessary to prevent self-immolation from loss of control over spells (though it's also shown black magic is still possible without it, and practice and discipline still allows one to be an effective black mage). The crystal for Summoner is a catalyst for the summoning of a primal's Egi. Physically-related jobs, such as Ninja, may describe certain techniques as being extremely difficult or impossible without their corresponding Soul Crystal, though some jobs will not offer an explanation for their Soul Crystal whatsoever. Dark Knight is functional without its Soul Crystal, as it shatters during the job's storyline (for gameplay purposes it is still whole and an equippable item) and needs to be repaired through absorption of the crystal's aether, but its state of disrepair has no adverse effect on the adventurer's techniques or capacity for them.
Some Soul Crystals may also contain the literal souls or consciousness of previous bearers, such as the Soul Crystal for White Mage containing the soul of A-Towa-Kant, the person to bear it before the Warrior of Light.
Etymology
The soul, in many religious, philosophical, psychological, and mythological traditions, is the incorporeal and, in many conceptions, immortal essence of a person, living thing, or object.