An immortal claiming to be thousands of years old, in the 1930s Yi Yang was head of the Dragon Tong, who smuggled drugs into New York City. Her operation ran foul of the vigilante Night Raven, bored thanks to her long life, instead of simply having him slain, Yi Yang exposed him to unidentified chemicals which rendered him immortal like her, but which also corroded his body and mind.
Wanting to add some psychological torture to the mix, after a decade or so, she gave a cure for the corrosion to some criminals, then made sure he word got out of its existence, but with the added lie that the cure was tied to a lethal plague; if Night Raven took it he would end his own suffering, but kill everyone he came into contact with. Despite this tale, Night Raven tracked the cure down and eventually, having deduced the plague story was false, took it. Over the next several decades he tracked Yi Yang, and they played a deadly game of cat and mouse.
In 1983 he blew up a boat she was on using a hand-held nuclear rocket launcher; she survived, but with the right-hand side of her body badly burned, leaving her permanently scarred and in pain. The pursuit continued, and in recent years Night Raven tracked Yi Yang to Russia, where he shot down a helicopter she was trying to escape in; as it crashed, she managed to pilot it to land on him, and both were caught in the resultant fireball.
Unsurprisingly given that both are immortal, neither of their bodies were found amongst the wreckage once the fire burned out.
Recently Yi Yang has resurfaced working with Contagion as one of his Unkillables.
Powers
Immortal, able to rapidly heal from even the most severe injuries, although the injuries are healed they leave scars. Severed body parts can reattach if in contact.