"Well, like you like to remind everyone, I'm half Luthor." Tess turned her head towards (Oliver), meeting his gaze head-on. Means I have the bloodright to rule this Circle if the reigning Luthor proves himself unstable to do what any leader must."
Tess speaking to Oliver Queen about Lex Luthor's poor decisions in regard to his Circle.
Chapter 27: Mirror, Mirror
Lutessa (Tess) Mercer is the bastard daughter of Lionel Luthor, sister of Lex Luthor, Julian Luthor and Lucas Dunleavy, and girlfriend of Oliver Queen. Since she is a part of the Luthor bloodline, she is apart of the Original Six Families.
Tess is described as being unemotional and withdrawn even in her romantic relationship with Oliver Queen. This is seen as a pure Luthor trait. She also did not inherit the Luthor ability to drain the life out of others.
Tess was raised in the Luthor family with Lex and Julian under the thumb of their father, Lionel. Eventually she joins in a Circle with Lex, Oliver Queen, Patricia Swann, Jason Teague and Davis Bloome.
She grew up believing that John Blackwell had promised her family his firstborn child, to use as a magical conduit.
Eventually, she and Oliver are sent on a mission and kidnapped by the Lost Boys via Patricia Swann. They are both tortured for information regarding the Balcoin Firstborn and they had their ring fingers cut off. She did not break from the torture. When they finally escaped (with Patricia's help) she and Oliver made their way back to Lex and had their fingers reattached.
They eventually made it to Smallville after surviving the mass murder of magical individuals which resulted in the death of Oliver Queen's parents.