Zero

Zero is what remains of Xion's soul, sharing his body with Zeroboros; his black wing represents Zeroboros while the white one reflects the remnant of Xion. He appears to seek someone to replace him as Guardian of End Earth and eventually chooses Souma, gives him one of the Twin Dragon Rings, and entrusts the world to him. Zero later revives Ryuna and Lazarus before leaving the group to watch over the world from afar.