Arceus is the God of the Meta-Universe and the Creator of all existence. As the Chief God of The Pantheon, Arceus stands as the most powerful being in existence and is feared and respected as such. He possesses the qualities of Omnipotence and Omniscience.
Arceus' birth from an egg triggered the beginning of the Multiverse as we know it. At first, it was complete chaos, and so Arceus made the Creation Trio: Dialga, to govern Time, Palkia, to govern Space, and Giratina, to govern everything in between. As precautions against rebellion, Arceus himself possesses the ability to overpower each of the Trio's control over their respective dimensions if necessary.
Arceus also created the laws of the Metaverse, he alone can create and destroy all matter and energy, as well as bend time and space. Arceus has a perfectly central moral compass, refusing to interfere in the affairs of the Multiverse unless it is threatened in any way. This does not include events such as the firing of the Halo Array, as events such as wars are ignored as they are a product of Free Will, which Arceus believes should be left alone completely. However, if an event should come about which would threaten the very existance of the Metaverse, like the Battle of the Distortion World or the Time War for example, then Arceus would send his Pantheon to intervene.
Arceus also created five lesser gods to govern different elements of life. Deoxys, Lord of Knowledge, to watch over and guide knowledge. Cresselia, Lady of Essence, governed the curing of diseases and the health of beings, Darkrai, Master of Dreams, governed Dreamworlds and the thoughts of mortals, Lugia, Lord of Creation, took over the job of creating new life and new things in the universe like stars, and Ho-Oh, Master of Destruction, was charged with keeping creation in balance by destroying things when their time in whis world is over.
Arceus' next supposed creation was Rayquaza, seperate from the Pantheon, but with great power and influence - the Lady of Life and Being, who governs life and death of all things. This one was kept concealed from the universe, allowed to work in secret, in order to better the experience of life for those who have the honor of enjoying it.
Arceus also had to outcast his son, Anarkhos, the God of Disaster, Chaos and Insanity, for his destructive inpulses. Anarkhos was Jealous of Arceus' glory but, being the merciful God that he is, Arceus decided to spare his son and simply outcast him to the Dark Space forevermore.
As the ruler of the Universe Arceus is also considered a Leader of the League of Utter Disaster, Chaos, and Insanity.