KOS-MOS is a combat android from the Xenosaga series, developed by Vector Industries' First R&D Division. She is equipped with advanced weaponry and possesses a highly sophisticated AI. Her primary mission is to protect the series' protagonist, Shion Uzuki. Throughout the series, KOS-MOS evolves from a cold, emotionless machine into a character with a deeper understanding of humanity. Her enigmatic nature and mysterious connection to the overarching plot make her a central character in the Xenosaga narrative, often serving as a bridge between the human and mechanical worlds.