Arceus is a super-ancient Pokémon rumored to be the first ever of their kind and be either the one behind, or the first result of, all Creation in the Pokémon World.

See also: Arceus.

It is said that in the beginning there was nothing, which exploded into an universe empty except for a singular Egg. From the Egg hatched Arceus and found themself alone in the Universe. Using the broken pieces of its Egg as a means to regulate their own power, Arceus shaped the early Universe and created six singular beings: the Creation Trio and the Lake Trio. Placing those entities in charge of sorting the Universe out, Arceus went to sleep for an undetermined amount of time.

Arceus is said to have seeded life unto a number of worlds or dimensions across the Universe, one of which would be the Pokémon World. Arceus themself would reside in a sort of “prime” world containing copies of all life, called the Museum Dimension.

Even the Creation and Lake Trios suspect Arceus to have been the first Pokémon ever as even they can not account for any Pokémon more ancient than them but Arceus.

Some religions in the world suspect the physical, llama-shaped Arceus to be an Avatar and the real entity be instead the Type Plates.

Arceus' capabilities are known to be tremendous in-universe, though no specific records of its boundaries or specializations exist. It is known that Arceus is very resilient, with attacks from singular highly trained Pokémon not able to faze it, and capable of extreme firepower, as its mid-tier techniques such as Flamethrower can knock back the likes of Mewtwo and taking a high-powered attack such as Hyper Beam from Arceus without some kind of barrier is inadvisable even for the likes of the Creation Trio. An undocumented battle suggests that it takes both Dialga and Palkia to block a portion of Arceus' signature attack, Judgment.

Arceus' body is tremendously resilient as would befit a creature capable of withstanding the times of early Creation. Still, the creature's known body is still physical and it has shown to take damage or suffer degeneration or deterioration over time; it is undetermined what if anything has been able to deal such forms of damage, nor what does Arceus to do recuperate, though this does give some credence to the belief that the llama-shaped body is only an Avatar of the real Arceus. If the rumor that Arceus brought the first humans into the Pokémon world by rescuing them from the collapsing side of a multidimensional black hole are to be believed, and assuming it would have used its real body, it suggests not even a crashing singularity can deliver crippling damage to Arceus.

Arceus' Plates can emit Typed Energy indefinitely, though due to their energetic frequency it needs to be filtered somehow for proper usage. Such power applied to a Pokémon can significantly empower their elemental abilities; the Plates are also tremendously stable and the power output and buffing can be maintained for near-geological times without needing any more intervention, behaving very close to a Perpetual Motion machine. Using the Plates as support Arceus can change type to increase its abilities and access specific moves of certain types, or even become completely impervious to some attacks. Due to the nature of Types in the Pokémon world, using a Plate to change its own type can allow Arceus to completely disperse the energy of some typed attacks like Draco Meteor; it is unknown if other Pokémon would be able to somehow unlock the same phenomena using the Plates as support, with the only experiment in producing a Pokémon with similar abilities, Type-Null, having been considered a failure.

Usage of even one of the Plates allows mortal but powerful Pokémon to perform tremendous feats. The ancient Volcarona ruler Tehra used one to maintain herself as the core of a superbiological Sun Machine, which sustained the needs of the underground world populations by nearly 700 years during the era of the “Rain from the Heavens”. After the crash between the ancient super-Pokémon at the end of the early Eras, the First Trainers used an undetermined Plate to bind and capture a member of the Weather Trio. It is also rumored that by using only the power of the Draco Plate, the Original Dragon was first able to split into the forms of Reshiram and Zekrom. Furthermore, combining a number of the Plates allows for the creation of artifacts of unrivaled reality warping power: the Jewel of Life, created by Arceus combining five of the Plates, was able to restore the natural lifecycle of the devastated Mishina region in only two years without any more intervention.

• Tail end of the second or third era of Ancient History, bringing the Human Species to the Pokémon world.
• Mishina ca. 3300 of the The Present Era.