First introduced in Mortal Kombat: Deception, The One Being is considered to be the origin of each of the Realms of Mortal Kombat: (Earthrealm, Netherrealm, Outworld, Orderrealm, Chaosrealm, Edenia, and others yet to be mentioned in the storyline). According to ancient legend, in the beginning of time, there only existed the One Being and the Elder Gods. The One Being fed off of the essences of the Elder Gods, but eventually, the Elder Gods defeated the One Being, and, in efforts to weaken the One Being's omnipotence, the Elder Gods separated the One Being's consciousness into the realms and created six Kamidogu, which held the essence of the One Being. The legend decrees that if one were to obtain all six Kamidogu with the Sacred Amulet, he or she would be granted ultimate power. In Deception, the warrior Shujinko undergoes this task through the guidance of Damashi, a spectre who, in fact, is a representation of the Dragon King, Onaga.
Because each realm is essentially a piece of the One Being's consciousness, the One Being flows through all life. The One Being uses the ambition of warriors such as Onaga and Shao Kahn in attempt to merge himself back together.
At the time of the universe's creation, there was the One Being and the Elder Gods. The One Being fed on the essences of the Elder Gods. In order to defeat the One Being, the Elder Gods created the Kamidogu and with it, they shattered its consciousness, creating what is now called existence.
For eons, the One Being's subconscious remained in a dormant state. It is unknown if the Dragon King was the first to serve the One Being's purposes, but because of Onaga's hunger for power, Outworld was created. After he died, Shao Kahn took control of the realm and continued his will by invading other realms and adding them to the Kingdom of Outworld. Through Shao Kahn's continued conquests, more of the One Being's consciousness would amass within the Outworld.
Shao Kahn and his forces were defeated during the invasion of Earthrealm, and thus dominance in Outworld dwindled; however, the One Being had other plans in the works as well. From beyond death, Onaga deceived Shujinko into traveling the realms and retrieving the shattered pieces of the Kamidogu. After a lifetime of searching, the Kamidogu were recovered, and with it, Onaga's means of returning to the living. Onaga traveled to the Nexus to thank Shujinko and then returned to Outworld.
Quan Chi was now the super power in Outworld; with the help of Shang Tsung, Raiden was defeated and Quan Chi then bested Tsung in battle. Onaga confronted Quan Chi and challenged his power – the sorcerer was no match for the Dragon King. Even as Shang Tsung and Raiden joined the battle, Onaga's power was too great. Onaga retrieved the ancient amulet he sought and now holds the key to shape the realms and become the One Being.
However, the Earthrealm warriors fought Onaga's armies. Shujinko, the very being who helped Onaga, fought Onaga himself. After a fierce battle, Shujinko, using the power of a thousand kombatants, defeated the Dragon King and destroyed the Kamidogu.
- In the Mortal Kombat novel by Jeff Rovin, the very first being ever to exist is called P'an Ku. It is said that all of reality, including all the realms and the other gods, are just a part of what was once P'an Ku. This was based on already existing Chinese mythology and the One Being's similarity to P'an Ku is probably coincidental.