Height: 107 cm
Weight: 18 kg
Summon: An extremely potent form of magic exclusive to Rydia. Calls upon the aid of phantom beasts from a distant land to do her bidding.
Story (contains spoilers):
Rydia was born in the village of the Misty Valley, home to the Summoners. The Summoners are a rare group of humans imbued with a very special gift: they can conjure phatom beasts from a distant land and have them do their bidding. However, the Summoner and beast share a strange bond; if the monster is ever killed in battle, then the Summoner will perish as well. Cagnazzo, under the guise of the King of Baron, orders Cecil and Cain to deliver a strange ring to the isolated village. On the way they kill a dragon that forms from the mist and hinders their progress. When Cecil and Cain arrive in the valley the powers of the ring cause the village to become bathed in flames; apparently Baron felt the Summoners were too dangerous to be left alive. Cecil hears the cries of a small girl and approaches them, to find Rydia and her dead mother. Rydia's mother was the one who summoned the Mist Dragon, so when the dragon fell in battle, the woman died also. Outraged to learn that Cecil and Cain were the ones who murdered her mother, Rydia summons a phantom beast called Titan which causes most of the valley to collapse in on itself.
Cecil awakens to find Cain missing and Rydia beside him, unconscious. Cecil takes the silent girl to an inn at the desert town of Kaipo where he encourages her to rest. That night an officer from Baron shows up at the end and demands the Cecil hand over the girl; Cecil's refuses, and proceeds to dispatch the officer and his guards. Rydia begins to trust Cecil at this point, a trust that is strengthened when he and Rosa help the girl to overcome her fear of fire.
While traveling by sea to Fabul, the boat is submerged underwater and Rydia is swallowed by Leviathan, a large sea serpent and (as revealed later) the ruler of the phantom beasts. Leviathan deposits Rydia in the Land of Phantom Beasts, where she perfects her study of the arts of magic. She shows up again in the underground world, just in time to save Cecil from Golbeza and his Dark Dragon. Notably, Rydia now appears to be a grown woman; when Cecil asks about this, Rydia explains that time flows differently in the Land of the Phantom Beasts (It is never explained, however, if she actually has matued both physically and mentally or if she is still something of a child in an adult's body). Either way, Rydia is much more open-minded at this point than she was as a child.
After defeating Zeromus, Rydia returns to live with King Leviathan and Queen Asura in the Land of the Phantom Beasts, perhaps able to relate more closely to the monsters with which she shares a psychic link than with humans since she had matured physically.