Tess Mercer is a fictional character from the television series Smallville, which aired from 2001 to 2011. She is portrayed by actress Cassidy Freeman and first appears in the show's eighth season. Tess is introduced as a complex character who works for Lex Luthor and later becomes the head of LuthorCorp. Her character evolves throughout the series, showcasing her intelligence and ambition. Initially depicted as an antagonist, Tess's motivations and backstory are gradually revealed, highlighting her struggles and moral dilemmas. She becomes a key player in the series' overarching narrative, particularly in relation to Clark Kent and the battle against various threats to Metropolis.