Weng-Chiang was an ancient Chinese god of abundance, having the power to make things grow. He was apparently an evil being, said to have breathed poisonous fumes from his mouth and killing men with white light from his eyes. A fanatical cult, the Tong of the Black Scorpion was convinced that one day he would return and rule the world.
51st century time traveller Magnus Greel was believed to be Weng-Chiang by Li H'sen Chang when he found him, and thus Greel gained control over the cult. (DW: The Talons of Weng-Chiang)