Draug is one of the Altean soldiers who fled to Talys alongside Prince Marth after their country was defeated by Dolhr and Gra. Some years later, Talys is attacked and its princess goes to Marth for help; Draug, following his lord's orders, enters the battlefield with his fellow soldiers. Once they have rescued the king of Talys and Marth starts his campaign against Dolhr, Draug follows Marth for the rest of the war.

(Source: Fire Emblem Wiki)