Mr. Wu (Keone Young) is the official or unofficial leader of Deadwood's substantial but mostly unseen Chinese ("Celestials") population, the Asian counterpart to Swearengen. He routinely interacts with Swearengen and other Caucasians over a few matters of business, such as the opium trade, and the seemingly daily efficient disposal of numerous human remains, through the route of his pigs. He knows almost no English beyond the words "San Francisco," "cocksucker," and "Hearst." He, however, communicates effectively with Swearengen (to whom he refers as "Swedgin!") with the aid of charcoal drawings and hand signals.
In Season 2, he becomes highly anxious over the arrival in town of the much more polished Mr. Lee from San Francisco, who appears to be the local representative of a large and shadowy tong organization allied with George Hearst, which henceforward supplies Deadwood with opium and low-priced Chinese prostitutes, from a new establishment to be called "Celestials' Alley", in partnership with Tolliver.
In the second season's final episode, Wu strikes back with the blessing of Hearst and Swearengen, slitting Lee's throat and leading Swearengen's crew to kill Lee's men. Swearengen strikes a deal for Wu to take over Lee's position of finding laborers for Hearst's mining operation, easily supplanting Tolliver in running Chinese affairs. In a symbol of loyalty to Swearengen, Wu slices off his braid (an action punishable by death in China at the time) and declares he will remain in America forever.
In Season 3, he returns from business in San Francisco wearing Western dress (which, as multiple characters remark, he looks terrible in). Wu had been tasked by Al with recruiting Chinese laborers in San Francisco to work in Hearst's mines. Sensing that Swearengen and Hearst have become bitter rivals, he holds the workers in another town rather than bring them to Deadwood. In the series finale, he brings his men into town in case the dealings with George Hearst take a turn for the worse.
See more photos of Mr. Wu here!