The Original One is a mythical story found in a book in Canalave Library. The story stated that Arceus created the universe and also created the Pokémon of time and space, Dialga and Palkia. The Original One also made Mesprit, the being of emotion, Uxie the being of of knowledge and Azelf the being of willpower.
This is what was written in the book, "In the beginning, there was only a churning turmoil of chaos. At the heart of chaos, where all things became one, appeared an Egg. Having tumbled from the vortex, the Egg gave rise to the Original One. From itself, two beings the Original One did make. Time started to spin. Space began to expand. From itself again, three living things the Original One did make. The two beings wished, and from them, matter came to be. The three living things wished, and from them, spirit came to be. The world created, the Original One took to unyielding sleep.."