|Alias(es)|| Tess Mercer|
|Appeared in|| Smallville: Absolute Justice|
Tess Mercer (born Lutessa Lena Luthor) is the younger half-sister of Lex Luthor. She took over LuthorCorp when he disappeared and through her encounters with Clark saw the light and became the second Watchtower after Chloe disappeared and moved to Star City.
One night, Tess went to her office at the Daily Planet and was shocked to find a chess-set piece on her desk. Tess then met with Amanda Waller at the Checkmate headquarters, who addressed her as "Agent Mercer" and said they had a lot to catch up on.
One morning, Tess was at the remains of the Luthor Mansion seeing the plans for the new project she would build on the site to help ease the Luthors history in Smallville when she was approached by Granny Goodness in a last attempt to recruit and "save" her. After refusing again to serve the dark, saying that she had decided to stay in the light, Granny reveals that Apokolips was approaching to earth and sadly gave her blessing to Lutessa.
Tess went to the Watchtower to see if what Granny Goodness had told her was true, but was surprised to discover that she could not access the satellites of the team. After investigating what was happening, Tess found that Oliver had disconnected the satellites to prevent them from noticing the arrival of Apokolips. Using the cameras of the space station that John Jones has just donated to the team, Tess discovered that Apokolips was above them and immediately went to tell Clark.
On her way to Smallville and because the communication signals were interrupted by Apokolips descent, Tess could not reach Clark and then she began recording a video to him, but in the process, she was hit by several armed men who kidnapped her.
Tess wakes up very confused in a laboratory and discovered that was Lionel who kidnapped her. He informed her that he had found the real Lex, who was regenerating himself all this time with the parts of the clones that were useful to him, and revealed that he plan use her heart as the last piece to resurrect Lex. Tess was quite scared when Lionel told this and try to escape but was stopped by Lionel's thugs.
Before beginning the surgery, Tess begged for her life again but without success and then finally break free using her fighting skills. She took a gun from one of Lionel's men, shooting her "father" in the chest before escaping.
After investigating the laboratory where she had been captive and finding no traces of Lex, Tess returned to LuthorCorp only to meet him in her office.
Lex reveals to her that he knew they were siblings from the beginning and that's why he was so confident in her. Tess revealed that nothing of that mattered now because she had not yet found her redemption. Lex stabs her in the abdomen after telling Tess he loved her. As she dies in her brother's arms, Tess touches Lex's face, affectionately at first, then wipes a neurotoxin on his cheek, a biochemical that removes all of Lex's memories up until that point. Lex told Tess that he was saving her from becoming like him, though Tess proclaims that Clark already has. Tess then died, finally achieving the redemption she'd always wanted.
- Kal-El/Clark Kent/The Blur/Superman - Her enemy turned friend and teammate.
- Lionel Luthor - Her father and enemy.
- Lex Luthor - Her half-brother, boss, and former love interest turned enemy.
- Chloe Sullivan - Her enemy turned friend and teammate.
- Lois Lane - Her employee and enemy turned friend.
- Oliver Queen/Green Arrow - Her enemy turned friend and former love interest.
- Carter Hall/Hawkman - Her enemy.
- Kent Nelson/Dr. Fate - Her enemy.
- Stargirl - Her enemy.
- Smallville (2 films)
- Tess's name is inspired by Eve Teschmacher and Mercy Graves, both loyal assistants of Lex from the 1978 film and Superman: The Animated Series, respectively, but the character is an original creation of the producers.
- Her middle name is from Lex's sister from the comics, Lena Luthor, who resided in Smallville up to when Conner Kent lived there.