This is about the anime character. For the monster itself, see Celious.
Together the three Centaurs guard the Fountain of Warriors, but when Gray Wolf defeats Centaur in a battle, Celious believes that he is bound by honor to stay and support his friend. Out of the three of them, Celious seems the most reserved and calculating, and when Centaur decides to challenge the Searchers to a battle, he faces off against Hare and wins.
The fights are interrupted by the Salamander troops, who burst into the coliseum to try to capture the Searchers themselves. Eventually, Celious and his companions change back over to the good side, and are seen fighting Moo's troops while the Phoenix is resurrected.
At one point, a flashback can be seen of Celious buying a flower in the town square from a young woman, and he appears to be flirting with her...