Arceus is a white, equine Pokémon with an androgynous appearance. It resembles a qilin or centaur with a gray, vertically-striated underside. The striated pattern has similar recurrences on the underside of its mane, tail, and face. Its four pointed feet are tipped with gold hooves. Its long mane juts away from its head, and its face is gray, with green eyes and red pupils, and a green circular pattern below its eyes. Arceus also has a streak of gold coloration on its head and ears that point upward. Its neck is fairly long, with two pairs of extrusions to the sides, and a flap-like feature on the neck's underside that is colored white like much of the body. Arceus also has a golden cross-like wheel attached to its body by its round abdomen, which changes color along with its eyes and hooves based on its current type, which depends on the Plate or type-specific Z-Crystal that it wields. The wheel also has four jewels attached to it. The pattern of striated gray of Arceus's underbelly resumes past Arceus's waist. Its limbs have gray undersides and extrusions at the tops of the legs. Arceus's tail is fairly like its mane in terms of shape and coloration. Despite its quadruped appearance, Arceus is capable of flight.

According to legend, it shaped the Pokémon universe using its 1,000 arms. Arceus has been referred to as "The Original One" in myths and legends and is generally considered to be one of the strongest Pokémon. Arceus is thought to have created Sinnoh and Ransei, and possibly the entire Pokémon universe, along with the lake guardians, , , and , as well as the Pokémon of Myth, , , and . Because of this, Arceus is thought to be one of the most long-lived of all Pokémon species. It has the power to recreate the Pokémon of Myth as well, presumably to guard the dimensions when a Trainer has caught one of them. In the anime, Arceus has been portrayed as having powers such as bringing back things that it once destroyed, making certain things vanish into thin air, halting time, and overturning the very laws of nature. The anime has also shown that Arceus has the power to not only calm Dialga and Palkia but also destroy the Red Chain. Arceus can change its type at will in order to adapt to a situation, as seen with its use of Plates (including the Legend Plate) or Z-Crystals. Arceus also has the power to split up into two, creating a piece of itself to exist outside of its home dimension which is also implied to be its physical form, being only a piece of its whole being, while its true form is unknown and incomprehensible.

Arceus is shown to care for and safeguard the planet in ancient times and protected it from cataclysms such as meteors, and it would show gratitude and compassion in return to those who treated it with equal kindness. In the modern time, Arceus continues to watch over the world, and it wishes for people and Pokémon to work together in the face of adversity. Even when it is needed, it would only give out hints for how to solve the problem, instead of directly interfering. In Pokémon Legends: Arceus, it is explained that Arceus can give its blessing to Pokémon to make them more powerful, which are referred to as noble Pokémon and Ride Pokémon, and the power is passed down through family lines. The people of Hisui worshipped the noble Pokémon. Arceus can also create items for humans to use, such as the Arc Phone. Arceus does not suffer fools gladly, and it will attack in a violent rampage if betrayed or deceived. It also holds long grudges if betrayed by those it considered friends. In Arceus and the Jewel of Life (M12), it is said to "feed" off the energy of the elemental plates. Arceus has the power to appear in dreams and create a variety of Pokémon to serve as challenges as seen in Eternal Battle Reverie.

In the introduction sequence of Pokémon Legends: Arceus, Arceus was capable of taking a large, golden, glowing, silhouette-like form while in its homeworld, it was shown to be capable of human speech, and it also states that Arceus is simply the name humans call it. The first ancient inhabitants of the Hisui region, the Celestica, worshiped it, referring to it as "almighty Sinnoh" and "great Sinnoh". Arceus also had the title "might of Sinnoh", with the term Sinnoh later on becoming the name of the region. The Diamond Clan and Pearl Clan also worship it, though they mistook Dialga and Palkia, respectively, for Arceus.

Forms
Arceus has eighteen different forms, one for each type.

(Source: Bulbapedia)