Rela Crystal is a recurring ability in the Final Fantasy series.
Rela Crystal is the most powerful magic spell in the game. It is a Holy-elemental spell and can only be cast during a boss fight with the Lich. During the fight, Chelinka or Princess Tilika will be standing nearby the party. When the player casts any magic spell, they will release a target ring to pile with the character's spell, casting Rela Crystal.