#493 - Arceus, Alpha Pokémon

Arceus made its debut in Arceus and the Jewel of Life. It was angry at the people of Michina Town for Damos's unwitting betrayal of it in ancient times, and so attempted to destroy the land. When Ash and his friends are teleported by Dialga to ancient times, they directly influence the event, changing the future for the better so that Arceus will stop its destruction.

In Battle Finale of Legend!, although Arceus is neither seen nor named, the Red Chain is said to contain the power of 'The Original One'. Using the Red Chain, Cyrus takes control of Dialga and Palkia by causing a red ring similar to the one surrounding Arceus' body to appear around their bodies.

(from Bulbapedia)