Eris Boreas Greyrat is a noble girl and distant relative of Rudeus. She is a tsundere with a short temper but has potential in the Sword-God style.

She is Rudeus' third wife and gives birth to their son Ars and daughter Christina. She is one of the three goddesses Rudeus worships in his religion. A wooden sword that serves as a relic for the Goddess of War is enshrined in the basement.