Galestork

Galestork is a Sacred Servant, one of the beasts sent down by God. It was sent to help Darwin seal Xizan and went afterwards to live in the Cave of Fear on the Western Continent. Baby had been left in this cave by Knight at the orders of the mayor of Orgo, but Knight went back to get it out of guilt. Galestork, having come back to its nest to find that Baby had eaten its egg, attacked Knight in a fit of rage.

Appearance
Galestork, as the name implies, has several stork-like qualities. When it's in battle, it stands with one of its long legs bent, much like a typical stork would do. It also has a long, thin neck and a long beak. It has several large feathers going back in a row on its head that are yellow at the bottom and gradually turn orange towards the top. On its forehead, just before those feathers start, is a green, rhombus-shaped gem. On either side of its face is a feather, much like the ones mentioned before, only larger in size. The torso has 3 wings on each side, each one's frame is white and the flight feathers themselves are yellow with red tips. The wings come out on both sides at the top shoulder area, just below that area, and then in the middle of the torso. Each wing is just a little bit longer than Galestork's whole body. For tail feathers, it has three long, ribbon-like feathers that start out white at the base and gradually turn yellow. The end of each tail feather has an orange oval and a smaller red one inside it.

History
Long ago, Xizan was summoned by the Kalajik, a notorious and evil race. God gave Darwin, a young man, the mission of going out to seal the great demon. In order to do so, he needed the protection of the Holy Armor and the help of the Sacred Servants, all bequeathed by God. Galestork, being one of the Sacred Servants, played a critical role in the sealing. The stone on its forehead has the power, when combined with the stones of the other Servants, to seal Xizan.

When or how Galestork was sent down and joined with the others is unknown, but from the video in the library at Picard, we're shown that Galestork, the other Servants, and Darwin all show up to seal Xizan as it's destroying an unnamed town. After the confrontation, the Servants all get into position and use their stones to form a pyramid shape with Xizan in the middle of it. This pyramid, made of a kind of crystal or physical light, seals Xizan inside it and shrinks down, small enough for Darwin to hold in his hand.

During Guardian's Crusade
After running an errand for the mayor of Orgo and bumping into a lost Baby on their way back, Knight is told by a mysterious figure, appropriately named "???", to take Baby back to its mother in God's Tower. Knight takes Baby with them, but decides to ask the mayor of Orgo for advice. At the orders of the mayor, who said that Knight was just imagining things and that it's not safe to have a monster in the village, Knight takes Baby and abandons it at the entrance of the Cave of Fear.

Later that night, Knight has a dream about the meeting with ??? earlier and wakes up feeling guilty and troubled about leaving Baby in the cave. They set out to go rescue Baby and follow through on the orders from ???. With no sign on Baby in the first few parts of the cave, Knight stumbles across the cave village of Kell and helps them out with a monster problem they were having. As thanks, they point Knight in the direction of an inner chamber where they had seen Baby go. Inside this chamber lives Galestork, who had been out when Baby had wandered into its nest and eaten its egg. When Knight finds Baby full and passed out in the nest, Galestork arrives at the scene and squawks at the intruders. It flies up to Knight and initiates a battle, only to get knocked out.

While Galestork is unconscious, Baby wakes up and gives Knight a green gem that had fallen from Galestork when it was defeated. Galestork is gaining consciousness at this point and starts to chase Knight and Baby, who run to the back exit of the cave. They stop, however, as that exit only leads to a cliff overlooking a river. Galestork emerges from the cave and is slowly flying up to them, but they fall off the cliff after trying to hang on to Nehani in the hopes that she could fly them to safety.

Galestork is missing for the rest of the game, having most likely abandoned its nest in the cave. However, once you have Chester, going back to talk to the villagers of both Orgo and San Claria will result in them saying that they saw a huge bird flying overhead and that they were worried Knight was eaten by it. This is before Xizan is unsealed and people start talking about a flying worm, so it is indeed Galestork that they're referencing.

Diving Beak
Galestork flies upwards and then straight down into the enemy like a torpedo. Rings of green light appear around its beak as it dives forward.

Power Gale
Galestork jumps in the air and hovers, its wings spread out and sparkling. Galestork fans its wings as they emit a flash and large rings of green light shoot towards the enemy.

Trivia

 * Although its element is wind, its name in German translates to "Firebird."
 * Galestork's gem isn't stated in canon as being any certain kind. Some people speculate that it could be emerald, though that theory clashes with the fact that Winged Lion's gem is confirmed to also be an emerald, albeit red. Some people opt to call it a peridot or some other precious green stone instead.
 * There is actually an error made during the Darwin Seals Xizan video in Picard. When the stones are used, they leave their owners for a minute. When they're returned at the end of the sealing, they fly through the air and back to the beasts, twinkling as they go. Ruval and Galestork's stones are mistakenly switched - the stone that goes back to Galestork twinkles yellow and the one going to Ruval twinkles green. Even the lights surrounding the Galestork and Ruval as they use their stones are switched!
 * Some of the stones used to make the buildings in Kell have a bird emblem. Depending on the timeline regarding certain events, such as when Galestork was sent down by God and when the buildings in Kell were made, it's possible that this emblem is a reference to Galestork.
 * The artwork shown in guidebooks and promotional items show that Galestork has very small and thin feathers in a half circle formation on its head compared to the thick ones going in a row as seen on both of the in-game models. The gem on its forehead in these pieces of artwork is also made very small for some reason, although it's roughly the size of Galestork's eyes in-game.