Julian

“I’m Julian! One of the bad guys! A Soothsire. Oh! Well, except I’m not anymore. See, now I’m a good guy! Lena gave me a reason to- well, let’s just say I’ve had a change of heart. Hm, not explainin’ myself very well, am I?”
— Julian, to Marth

Julian (Japanese: ジュリアン Jurian) is a thief hailing from Macedon. Formerly a member of the Soothsires, the bandits dominating the Samsooth Mountains, he turned on the group upon encountering one of their prisoners, Lena, and escaped the group with her, soon joining Marth's passing army.

(Source: Fire Emblem Wiki)