Zelgius was born in Daein. However, while growing up, he had a miserable childhood because he was a Branded, with the mark being on his back (according to him, someone on his father's side was with a laguz). Because of this, he was looked down on and hated by his own family. This prompted him to leave home and join the Daein army in order to escape his suffering. He feared being discovered and treated the same way by his new comrades so he attempted to hide his brand by rarely removing his armor even when indoors. When he discovered that the brand also slowed his aging, he knew that his time in Daien would not last and he would eventually have to leave to preserve his secret.