From ROI Wiki

Segarg is a demon of Verok and Negago's chief demon in charge of his army. His executive officer is Regnig. He is an insanely powerful, muscular creature with great black wings and a massive, devastating, and intimidating sword that he carries in a large sheath on his back. He is a master of combat and a master of strategy as well. He is one of the first demons to fall after Negago's rebellion and has been Negago's right hand man since the beginning. Only towards the end of the series does he begin to see the error of his ways and seek repentance and restitution for all of his many millennia of crimes. And, even if doing so won't keep him from his ultimate punishment in Verok, he vows to make right all of the evil he did, one way or another. As part of his efforts to do this, he allies himself with Tgegani and the other Burgon Lions to protect their people from destruction.