Cassios, a native Grecian, trained in Sanctuary under the guidance of Ophiuchus Shaina. He had a reputation of being a brutal fighter who enjoyed making his opponents suffer. Cassios was a top contender for the Pegasus Cloth, and went up against Seiya in the final round of the competition, having won nine consecutive rounds. Cassios seemed to have the upper hand, being nearly twice Seiya's height and three times his size. He boasted that he would start the match by cutting off Seiya's ear, but before he could strike, his left ear was cut off by Seiya. He was quickly defeated by the Pegasus Ryu Sei Ken.
Cassios never forgave Seiya for his defeat, believing that, being a Grecian, the Cloth was his by right. His hatred was compounded by the fact that Shaina did not return his love, but loved Seiya instead. During Seiya's battle with a brainwashed Leo Aiolia, it appeared that Cassios would attempt to stop the other Bronze Saints from coming to his aid. But Cassios proved to be more noble than he seemed, deciding to save Seiya for Shaina's sake. He allowed Aiolia to kill him, thus freeing the Gold Saint from the Pope's control. Seiya wept at his old rival's death, saying that perhaps Cassios could become a star to protect Shaina.