Sefa is a young maid who was working as the personal servant to Queen Guinevere Pendragon. Sefa secretly spies for her father, Ruadan, an ally of Morgana Pendragon. When she goes to tell her father that King Arthur is planning to ambush Morgana's army from Queen Annis's kingdom, Gwen sees her leave the castle. At first, Guinevere merely thinks that she is going to see a boy she has feelings for, but later figures out that she is a spy when Sir Leon and Sir Elyan return to Camelot and tell her Morgana ambushed them, meaning that someone told Morgana their plans and Sefa was present at that time. When Sefa is brought to the court, she reluctantly confesses her treachery, saying that her father should be respected, despite having magic. The queen is furious by Sefa's betrayal which has lead to the deaths of many good men, and sentences her to death.
Gaius later visited Sefa in the dungeons and she convinced him to allow her to speak with Gwen. She tried to persuade the Queen to change her mind about her sentence, but Gwen told her that her decision was final. After Sefa was taken away however, Gwen revealed to Gaius that she actually had never intended to execute Sefa. It was a plan to lure Ruadan to Camelot. When Ruadan arrived to rescue his daughter, he fought off many knights all by himself but was fatally wounded by Sir Elyan. Sefa and her dying father managed to escape and Ruadan told her to send word to Morgana. He then told her he loved her and died. As Camelot's knights closed in, Sefa fled and her current location is unknown (Arthur's Bane).
Sefa has a very different personality from Morgana and Agravaine, who were previously spies in Camelot. While both of her predecessors had been malicious and manipulative, Sefa was shy and showed no signs of being evil. The only reason she was a spy at all was because Ruadan was her father and she was more attached to him than to Camelot. When Ruadan was stabbed by Sir Elyan, Sefa helped him escape Camelot (ironically he had been the one who was supposed to rescue her not the other way around). She later begged him to try and heal himself and was devastated when he died.
Sefa was uncertain about whether she was doing the right thing by spying on Camelot, saying that the people of the kingdom had been kind to her. When Guinevere revealed to her that many men died because of her, Sefa was at a loss of words and was clearly distraught at this thought, meaning she was sensitive about the matter of causing the death of many people. Another difference between Sefa and other spies of Camelot is that she is more honest and a considerably worse liar than the previous two. She admitted to her father that she was being treated very well in Camelot, and when Guinevere asked Sefa if she had betrayed them, she didn't try to convince the queen otherwise for long.
Sefa had a good relationship with Guinevere until the latter realized she was a traitor and she used to treat her like a friend instead of a servant. Even when Gwen sentenced her to death, Sefa showed no hatred, merely remorse about the fact that her actions could have gotten people killed. She was also remarkably calm when the guards were dragging her down to the dungeons and didn't beg for her life or even show any defiance, accepting her punishment without a word. However during the time she spent in the dungeons, Sefa became frightened of her execution and persuaded Gaius to allow her to speak to Gwen so she could plead for her life.
- Sefa did not appear again on the show after Arthur's Bane. It is unknown what became of her after her father's death. Perhaps, Guinevere forgives her, knowing that Sefa has been manipulated by Morgana and Ruadan, and she returned in Camelot after Morgana's death.
- It is unknown if Sefa has magical powers, it could be assumed that she does by the fact that her father used magic and was a druid.