Tess Mercer (born Lutessa Lena Luthor) is a villainess in the show Smallville. She is both the former protégé and half-sister of billionaire Lex Luthor. When Lex Luthor disappeared during a private expedition to the Artic, Tess took control of all his projects and business. Like her predecessors Lex and Lionel, she became obsessed with finding the truth about Clark Kent (Superman). She had very little touch with everyone who knew Clark, including Chole Sullivan, Lois Lane and her old flame Oliver Queen, who did not have any confidence in her due to being an emissary of the Luthor family.