Gareth

Gareth ​is a non-playable character in Fire Emblem: Path of Radiance, and an enemy/playable character in Fire Emblem: Radiant Dawn. He is a member of the Red Dragon tribe of Goldoa, and body guard to King Dheginsea or any royal retainers in need of personal guard (as seen when he stayed near Prince Kurthnaga in their first appearance). He is notably wider-set than your average Red Dragon, and, upon transformation, he is bigger and of a darker hue than most Red Dragons (or any dragon, for that matter).

Gareth is a loyal member of the Goldoan Royal Court. Although it is not clearly mentioned, he is a high-ranking member of the court and a retainer to both his King and Prince Kurthnaga.

Path of Radiance
He is seen with Prince Kurthnaga in Fire Emblem: Path of Radiance. As the Greil Mercenaries were traveling with Princess Elincia to the theocracy of Begnion by ship, they were run ashore by Kilvan pirates. The shore they so happen to dock upon was none other than the solemn dragon country of Goldoa. They were hailed by Black Dragon prince Kurthnaga as he was strolling along the coast with royal retainer Gareth (as well as his own personal guard). After an exchanging of word and traveling gifts from the prince, the mercenaries were on their way. This is the only appearance of Gareth in Path of Radiance.

Radiant Dawn
After the Mad King’s War, Dheginsea revealed the truth behind his isolationism to the other dragons, earning him their and Gareth’s absolute obedience. He appears during the third part of the final chapter, standing with King Dheginsea, Nasir, and the rest of Goldoa against the warriors of Yune. When faced with having to fight the king’s beloved son Kurthnaga, who refused and opposed Ashera’s judgement on the world, he fulfilled his duty as a member of the dragon tribe in accordance with Dheginsea’s wishes and stood in the way of Ike and company in the Tower of Guidance, as Ena and Kurthnaga are both able to speak with him, yet neither are able to sway him to their side.

He will join you if you do not kill him during the battle against the dragons.