His default name is Ryu, the Japanese word for Dragon. He is the Destined
Child, scion of the Dragon Clan, and wearer of the Dragon
Jewel.
As you may guess, he's pretty freaking' important.
Ryu is your starting character, and he will always be in your party; there's
only two exceptions to this the whole course of the game.
Fighting/Defense -- Ryu is a very tough character; only Katt's shamanized form can top him in sheer damage, and only Rand can top him in defense. Ryu also has high HP, and is one of the two characters who can counter-attack when hit. When is his condition is Super, he'll make a critical hit every few attacks, and is just as likely to counter-attack. He is somewhat slow, however. He uses swords, some rapiers, and some knives. He can use most armor.
Special -- Guts. The higher Ryu's Guts score is (the more flames there are), the more HP he can recover using this. The less HP he has remaining, the more he'll regain when you use it. However, it'll restore less HP each time you use it in the same battle. I myself don't recommend using it unless you've exhausted your healing item stores. It'll never match a Roast or Extract.
Magic -- Ryu has little AP, and can learn only a few spells via gaining
levels. Smoke and Time Warp are unique to him. His real power
-- and what makes him your most powerful character -- are his dragon spells.
You must have full AP to do full damage with these, and you expend
all AP when when you use one. That low AP is a blessing.
Puppies: Fire, Ice, and Thunder. They do 256 damage (about equal
to a critical hit with BoltX) to a single foe, and are elemental in nature.
Resistances and vulnerabilities to these elements apply.
Dragons: Once again, Fire, Ice, and Thunder. They do 512 damage
to all enemies, and are non-elemental. A monster resistant to or weak
against fire still takes 512 from the Fire Dragon.
G. Dragon: 999 damage to all enemies. Non-elemental. The
ultimate crowd cleaner and boss killer.
There is also another power he gain gain, called Anfini, but that'll be covered
in the walkthrough section.
Shaman Forms -- None.
Field -- Ryu can fish. If you see a leaping fish when you are wandering the world, put Ryu in the lead and have him "talk" to it. With a rod and the right bait, Ryu can catch some fish. Use Worms to catch Sardines, Unagi, Bait, and Mackerels. Use Urchins to catch Tuna, Minnows, Pile Worms, and Snappers. Shrimp can used to catch one of those last two (I can't remember which), but it really has a another purpose. Gold can catch the fish-man Marinero. G8Bait can be used a substitute for anything other than Gold. Using the Charm Rod (or Deluxe Rod, though it'll be much harder) and any bait, Ryu can also "catch" and reel in a treasure chest -- this is the only way to get Ryu's best sword and armor.
By the end of the game -- Ryu is one of your powerhouses, and will have all of his powers by this time. He and your healer will be about equal is crucialness to victory.