Throughout the game the protagonist, Vyse, is the character that is actually controlled by the player. Vyse and Aika, the female lead, are permanent members of a four character party. A short way through the game, Fina changes from a storyline-only role to a playable character and a permanent member.
Vyse: A Blue Rogue (air pirates that only attack armed vessels larger than their own ships, in particular those of the Valuan Armada). Vyse has an upbeat, optimistic personality and refuses to give up. Sometimes, he is the one who keeps the entire party's spirit up. He is also the character the player controls when not in battle. Vyse fights with twin cutlasses, one primarily used in offense and one for defense.
Aika: Vyse's close friend since childhood and fellow Blue Rogue. Aika has a strong personality and an easily inflamed temper, yet has weaknesses such as obsession with treasure and fear of swimming. She also orphaned at an early age, and was cared for by Vyse's family. Aika fights using an oversized boomerang. Aika has problems with authority figures, but comes into her own when she, Vyse and Fina strike out on their mission.
Fina: A "Silvite" (survivor of the ancient, defunct Silver Civilization). Fina is sweet-natured and demure, but hides an iron will. Fina's pet, a silver ball-like creature named Cupil, fights for her. Cupil can morph into various shapes, and gains power by eating Chams, Moon Stone shards that are hidden throughout the game. His most powerful form is Final Cupil. When not in battle, Cupil takes the form of a bracelet that Fina wears.
Secondary player characters
Drachma: A 55 year old maimed man, Drachma lost his right arm, eye, and son whilst fighting the giant arcwhale Rhaknam. He now has a mechanical right arm which he uses as a weapon during battle. His obsession with hunting Rhaknam leads him to search the skies. Drachma is the captain of the small fishing airship, Little Jack. He travels with Vyse and the others for part of the game, and pretends not to care about them, but he shows up just in time to save them quite a few times.
Gilder: A rakishly handsome 32 year old man, Gilder wears a pince-nez and uses a pistol as his weapon. Gilder is the captain of the light, swift pirate vessel Claudia. He has a parrot named Willy, who can be helpful when Gilder needs to break out of jail cells. He is a very laid-back individual, and loves good times and women. However, he seems to be constantly looking over his shoulder and running away from Clara, a Blue Rogue obsessed with Gilder.
Enrique: At 25 years old, the Crown Prince of the Valuan Empire, but disagrees strongly with the imperialist policies of his mother, Empress Teodora I. The name of his father is unknown. Enrique uses rapiers as his weapon in battle. He joins the party and gives Vyse his flagship, the Delphinus, when he escapes Valua with Vyse, Aika, Fina, and Gilder. His frank nobility and chivalry are in direct opposition to the attitudes of most of the higher Valuans, and it is his infectious goodness that ends up saving the entire party later on.Antagonists
The Blue Rogues' sworn enemy, the Valuan Empire, continually hunts Vyse and Aika throughout the game. The Valuan Empire is ruled politically by the Empress Teodora I, but the real military power lies with the Lord Admiral Galcian. Galcian's five deputies - Alfonso (First Admiral), Gregorio, Vigoro, Belleza, and De Loco (Fifth Admiral) - each have a distinct personality, personified by their highly unique flagships. Amongst themselves they are each silently competing for promotion at the expense of the others, especially Alfonso, who thinks he should be Lord Admiral instead of Galcian. Galcian's Vice-Captain Ramirez later becomes the Sixth Admiral of the Valuan Armada and has a mysterious connection to Fina.
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In addition, a significant number of lesser adversaries confront the player throughout the game. These are mostly 'Black Pirates', a faction of unscrupulous criminals who lack the Blue Rogues' self-restraint and hence have earned the Rogues' ire. Notable Black Pirates include Captain Baltor, a bandit from Nasr airspace who pursues a small vendetta against Vyse, and Gordo the Round, an obese pirate whose plundering is driven by his lust for unique food. In the Gamecube re-release, several more of these Black Pirates appear and can be hunted for bounty rewards, including a trio of criminals who resemble Vyse, Aika and Fina in appearance and poison Vyse's reputation unless defeated during an optional sidequest.
Text from Wikipedia.org