Cellvanta Grathan was a Sith female Human. She was married to Grathan, the rebel Sith Lord within the reconstituted Sith Empire, and was also the mother of Beelzlit Grathan.
In the year 3643 BBY, she resided on Dromund Kaas at her husband's estate, remaining there with her son. This lasted until Darth Baras' apprentice arrived with orders to eliminate Beelzlit. Cellvanta made an attempt to shield her son from the Sith, urgently telling him to flee. However, Beelzlit chose to fight in order to defend her. The two of them engaged the Sith Warrior, but were easily overcome.
After being severely beaten, Cellvanta pleaded for her life, desperately asking what she or her son had done to deserve this. Realizing that her husband's political dealings had embroiled both her and Beelzlit in the Sith's affairs, she attempted to negotiate with the Apprentice. In an effort to save her son, she offered the Sith Warrior her husband, Lord Grathan's, life in exchange for Beelzlit's. The Sith Warrior declined her proposition and instead opted to kill them both. Once again, Cellvanta urged her son to escape, but Beelzlit chose to stay and die with her. Before she could react further, Cellvanta was stabbed by the Sith Warrior.
If Cellvanta is spared as a light side choice, she will persuade the Sith Warrior to murder her husband, allowing her son to assume his position. If the Sith Warrior is male, she will offer the Sith apprentice an "intimate" encounter after he kills Grathan. She would then send a gift to the Sith Warrior by way of Ralesk, her former husband's most trusted assassin. Unbeknownst to her, her son had also instructed him to silence them, so his secret identity would remain hidden. Ralesk's attempt is unsuccessful, as he is defeated by the Sith Warrior, leaving both intentions unfulfilled.