Ceres (spelled Cérès in French) is the last surviving member of the Mong people, a very ancient race.
Embittered due to centuries of loneliness, Ceres takes part in the race for the sake of blocking the way for the other candidates more than for anything else. For Ceres, none of the people expanding in the galaxy are worthy of the Ultimate Prize.
Ceres raced against the Earth Team in Cruel Like Ceres. He was able to trap Molly within a hallucination during their race, until Rick was able to turn on her CD player, the loud rock music caused the illusion to shatter and Ceres to lose concentration and ultimately crash into a wall on the race track.
He survived the crash somehow, and is briefly glimpsed in Make Way!, waiting in line to return to his homeworld.