One Being

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.

Although the storyline of Deception would seem to hint that the One Being would be the villain of the next title, Mortal Kombat: Armageddon, this was later proven false, as Blaze would end up as the final boss in this game. The One Being is only mentioned twice in Armageddon: once in a passing statement about the kombatants "tapping into the power that make the realms", which may or may not refer to the One Being, and more directly by name during Kai's game ending.

Powers
From the fact that it fed off of the essences of the Elder Gods it could be concluded that the One Being holds the powers of each Elder God giving it omnipotence. It could also be concluded that it has control over time/space, reality, and all lives within the realms.