Courtesy of Bulbapedia Arceus
(Japanese: アルセウス Arceus) is a Normal-type legendary Pokémon. However, its type will change when it is holding one of sixteen items known as plates and can in reality be any type.
Like Darkrai and Shaymin before it, Arceus was not officially recognized by Nintendo until February 2009, the year of its debut movie. It was later revealed by the official site on August 3rd, 2009.
Arceus is also known as "The Original One," as it is said that it created Sinnoh, and possibly the entire Pokémon universe, along with the lake guardians and creation trio. Arceus can only be found in the wild legitimately with the Azure Flute, which has not yet been distributed officially and can currently only be obtained by cheating.
However, Arceus itself was distributed via multiple Nintendo events in 2009 and 2010.
in Pokomum's case i see where you're going and i hope you get to Legitly catchem all