P'an Ku is a non-canon character that made his one and only appearance in Mortal Kombat (novel). He is remarkably similar to the One Being who wasn't introduced in the games until Mortal Kombat: Deception. He existed before all else in the universe. It said that he one day simply willed himself to exist. However, he eventually died, though not entirely - as every part of him makes up the very fabric of reality. There is a poem to describe P'an Ku in the novel:
He cannot die yet does not live, 'tis true.
He is more than all, and all is P'an Ku.
His left eye became the sun, his right eye became the moon, his flesh became the living earth, his blood became the rivers, his hair became the forests, his dying breath became the wind, his last groan became the thunder, and his soul became the god T'ien.
The chambers of P'an Ku's heart radiated auras of white, black, blue, and red. Each of these chambers were actually portals to different realms - the white for the heavens, black for the realm of the dead, blue for Earth, and red for Outworld.
P'an Ku is based on the legend of a titan in Chinese mythology.