Kain and Able -- They're brothers and have been friends with Marth for a long time. Able is sort of Sain-ish and has a way with ladies. Kain's more serious, but can show a droll sense of humor at times. Kain's the older of the two.
Jeigan -- He's got multiple jobs connected to Aritia's Royal Family. He's been a longtime friend of King Cornellius (Marth's Dad) and is extremely loyal to him. He also helped, to a certain extent, raise Marth when his Father was too busy. In book 1, he is commander of Aritia's knight troops, and also a partial advisor to the king. In book 2, he retires from knighthood and remains as an advisor to Marth.
Doga -- Doga's been in the Aritian army for a while and is commander of the armor knight troops. He's real quiet and down-to-earth. I think they portrayed him perfectly in the anime when he was reading a book. I'm not sure if he has a relation to Gordon or not, but he tends to look out for Gordon and protect him, likely because he's so small, young, and inexperienced.
Gordan -- Gordan's a rather new recruit to the army and lacks battle experience. He's very energettic and willing to lend a hand, and sometimes acts as a sidekick to Doga. I *think* he might be in a similar situation as Kashim and joined the army to raise money for his family, but I'm not sure.
Oguma -- Oguma was previously enslaved by Doluna and was beat horribly durring his time there -- as a result, he has a nasty scar on his left cheek. Durring a slave auction in Norda, Sheeda saw him hurt and bleeding and begged her father to buy him. The King of Talis did so and took him in, not as a slave but as a soldier. Oguma has since then become unbreakably loyal to his saviors and the captain of Talis's army. His main duty is to act as Sheeda's bodyguard.
Navaare -- They keep Navaare's background a secret on purpose. He's supposed to be mysterious. All I know is that he became a wandering mercenary after somebody killed the woman he loved. He's not exactly sure why he joined the bandits on Devil's Mountain, but after seeing Julian's relationship with Rena, he decided he would aid them (at least a little) so Julian wouldn't have to go through what he did.
Kashim -- Kashim's a poor boy from Grunia who joined the army because his mother was dreadfully ill and needed medicine, but they had no money. (Sound familiar? Dorcas and Natalie?) He hoped to raise the money in time, but Sheeda gave it to him instead and he has since then vowed to protect her with his life.
Maric -- Maric's been a long time friend of Marth's, despite their age difference, and has always been fond of his sister Ellis. For a while he was in service to Castle Aritia, but left to further his magic studies in the Khadin Academy. He is always thirsting for more knowledge in the subject of magic.
Rena/Lena -- Rena is one of the most selfless and powerful nuns in the Macedonian Monestary. She left on a pilgrimage some time ago in order to aid the needy and ended up getting captured by the Devil Bandits while out gathering healing herbs. Whether they plan to sell her or use her as a whore is unclear, but Julian was disgusted by her treatment nevertheless and rescued her.
Julian -- As far as I know, Julian's been a rogue all his life. He's a bit of a wanderer and doesn't really know which path he wants to follow. However, Julian's not cold-hearted like most bandits and is quick to fall in love with Rena when she's captured and brought in to the hideout. He often slipped her food and water while he planned in the meantime to set her free. Eventually he managed to betray the bandits and escaped with her, and has since then dedicated his life to more chivalrous services.
Minerva -- Minerva is the middle sibling of the three heirs to Macedonia's throne. She is very intelligent, and often matched wits against her brother Michael in topics such as logic, politics, and the like. She went out of her way to take care of both he and Maria, and it was her love for the both of them that kept her trapped in servitude to Medeus after Michael killed their father and usurped the Macedonian throne in Doluna's name. She's not a very good ruler at all, but she has a strong sense of justice.
Maria -- Not much info on Maria. She's the youngest sibling of the heir trio and a gifted magic user. That's about it. Doluna captured her and held her hostage in Deal in order to manipulate Minerva. If Minerva didn't do exactly what Doluna wanted, Maria would be killed.
Linda -- Linda is the only daughter to the Great Sage, Miroa. Miroa was known as the Sage of Light, and was an avid student of Gato's. She also knew Garnef, but Garnef went crazy, stole Maph, and killed Miroa with it. Knowing she was powerless to do anything, and that she'd be hunted by Garnef as well, Linda disguised herself as a boy and ran away, only to be captured by the slave sellers in Norda. Marth freed her and she has since then become loyal to Aritia and a close friend of Maric's.
Medea -- Medea is one of Bares's top knights and helped to guard Princess Nina. She grew up with Astoria and George, but loves Astoria. Boa has been her mentor for a long time.
Paola, Katua and Est (yay!) -- Paola, Katua and Est are all nobles from a tiny northern kingdom that was destroyed in Michael's search for Aoite's shield. (I think) Michael captured them and forced them into service for Macedonia when he saw their skill as pegasus knights. Paola took pity on Minerva's plight and became loyal to her, with her sisters following suit. In turn, Minerva premoted them to rather high ranks in the Macedonian army. The three pegasus sisters have a very strong bond, and Paola always looked for a way to free her two younger sisters from their slavery in Macedonia. When she realized Marth was the answer, she spent a long time searching for him, but she and Katua were seen as potential rebels and exiled from Macedonia to Gra. (Est had disappeared). Paola is the oldest, Katua is the middle sister, and Est is the youngest.
Chiki -- Chiki is the daughter of the Mamcoot King, who was killed by a power-hungry Medeus seeking his throne. Banetou, her grandfather, ran away with her and took refuge amungst a small Mamcoot tribe so she would be protected. Chiki is adored by her people and, being the legitimate heir to the throne, is seen as their only hope. Unfortunately, Medeus knows this too. He decides to take advantage of her amazing power and kidnaps her from Banetou. Garnef places her under a spell so she thinks Medeus saved her from the
"real" person who killed her father, and she serves him until Banetou can snap her out of it. She is also quite fond of Marth, but who isn't?
Ellis -- Not much on her, either. She's Marth's older sister and she loves her little brother to death. When Doluna invaded Aritia, Jeigan tried to escape with the both of them but they got cornered. Ellis gave Marth her tiara (afraid she was going to die/never see him again) and then warped both he and Jeigan away to safety, allowing herself to be captured. Garnef has a strange fetish with her, and Medeus wants her to suffer because she is a descendant of Anri. Maric is quite in love with her, but I can't tell if she loves him back or not. I'm pretty sure she does.
Camus -- Camus is the son of a wealthy Grunian lord who has always been loyal to King Lui. He joined the Grunian army at a young age and quickly flew up the ranks because of his immense skill as a knight. (Eventually, he became commander of the entire army) It was this skill that Medeus sought, and he threatened to obliterate Grunia if Camus didn't join his cause. Grudgingly, Camus agreed, unwilling to endanger the people of his beloved country. Some time later, he was sent to Bares to conquer the capitol and murder the Royal Family. But in the midst of all the bloodshed, he took pity on Nina and helped her escape. She immediately fell in love with him, but it took him a while to feel the same for her. Camus is a very sad and melancholy person in book one, constantly regreting every move he makes in the name of Doluna. In book two, he's mended his ways and is ever-valiant, fighting in the name of Akanea's royalty.
Michael -- Michael is a Marquess Laus figure. He is power hungry, and easily manipulated by Doluna. Garnef (I think) eventually convinced him to kill his father and become King of Macedonia in his stead. He sought to marry Rena, but she refused and fled the country. Needless to say, he was quite pissed, so he forced her brother Marchis into the army. Minerva protested against his sudden rebeliousness, but to quiet her he imprisoned Maria and forced Minerva to do his bidding. For some reason, he's pretty good friends with Camus. After Marth's army comes through and defeats him, he fakes his death and exiles himself. It takes him some time to mend his ways, but eventually his love for his younger sisters overcomes all else and he returns in time to save at least one of them.
I hope this helps. If you have any other questions, don't hesitate to ask.
The above is pretty much all I know about each character, though...
