Paipu is a non-canon character that made his only appearance in Mortal Kombat novel. He is introduced to us as the uncle of the Great Kung Lao and husband to Chen Lao. Paipu was a tax collector by trade, but in his free time worked on experiments involving the gods and the dead. When his brother Wing Lao died in an explosion, he and Chen were left to raise Wing's sons, Kung Lao and Chan Lao. Paipu did not want the responsibility of raising his nephews, and Chen was trying to get him to stop doing his experiments, which she claimed were unsafe and would be an unhealthy environment to raise their nephews in. One day, while Paipu was out collecting taxes in the town of Amiko, Chen sold his potions, jars, powders and scrolls, hoping to end his experiments. However, the citizens of Amiko did not wish to pay their lord prince and beat Paipu to death.
Or so the reader is led to believe. It turns out that prior to his birth as Paipu on Earth, he was a demon born in the Outworld as Shang Tsung. He had been born and reborn on Earth, many different times, sent by Shao Kahn to open up the portal between Earth and Outworld. Paipu's need to experiment and seek the answers to the great mysteries of life were actually the result of visions and dreams given to him by Shao Kahn. When Paipu learned of Chen's actions, he faked his own death, resumed his life on Earth fully now as Shang Tsung, escaped to his own private island called Shimura, and worked for years finally discovering a way to open the portal to Outworld.