Kartik (born in Bombay, November 10, 1878) is one of the antagonists of Libba Bray's A Great and Terrible Beauty and is a protagonist of The Sweet Far Thing, he is both an antagonist and protagonist in Rebel Angels. He is the younger brother of Virginia Doyle's (Gemma's mother) protector, Amar.

In A Great and Terrible Beauty, he is initially a member of the Rakshana and is given the task of watching Gemma Doyle and preventing her from entering the Realms. He lives with the Gypsies who camp on the grounds of Spence Academy, a girl's boarding school which Gemma attends. He shows an interest in Pippa Cross (Gemma's friend, very beautiful), but also shows a slight interest in Gemma. They share a kiss later in the novel, to show the other Gypsy men that Gemma was with him, which would allow Gemma, Ann and Felicity (Gemma's other friends) through to see the Gypsy elder/psychic Mother Elena. When Pippa dies, he visits Gemma at Pippa's funeral, and they share a tender moment. Having failed his mission, Kartik is called back to London to be reviewed by the Rakshana.

In the second novel, Rebel Angels, Kartik is given two tasks by the Rakshana, after having failed to stop Gemma from entering the realms. First,he must convince Gemma to find the Temple of the Realms (the source of the power in the Realms), and bind the magic to the name of the Eastern Star, which is the Rakshana. He is told to woo her, if it proves difficult for him to gain her trust. His second task is to kill her. In order to keep an eye on Gemma, Kartik becomes a driver to the Doyle family over the Christmas holiday when Gemma returns home, but begins to fall in love with her. Gemma is being courted by another young man, however, and Kartik's advances are continually rejected, though Gemma spends a good deal of her time thinking of him. He continually tries to warn her by giving little hints about his second task. Then Gemma determinedly ignores his final plea for her to come and talk to him of something important. Afterwards they go to save Gemma's father together and get to know each other even more. Later they end up dancing together and end up kissing. She then accidentally insults him after they have another tender moment together, he leaves, hurt, and returns to the Rakshana. Later on, Gemma is kidnapped, and he comes to her rescue, leaving the brotherhood of the Rakshana and putting himself in mortal danger. He later decides to form an alliance with Gemma and her friends.

Kartik's absence at the beginning of The Sweet Far Thing does not go unnoticed by Gemma. His return to Spence brings about bad news for Gemma, for he says that he does not wish for their lives to cross again. He reveals that he will go sailing, and Gemma is hurt by this. They have several romantic little encounters, through which it is clear that they both want very much to be together. Gemma learns that Kartik is determined to leave her, however, because his late brother Amar appears in his dreams insisting that he will put Gemma in mortal danger. However, when the Rakshsana threaten Gemma's brother and she sees Kartik'sbrother in the realms, it convenes him to stay in order to see Amar and try and save his brother's corrupted soul. Gemma blackmails Kartik into arranging a meeting with the Rakshana, after which a brief battle with Fowlson ensues, which essentially brings to light much information about Kartik, and brings the two closer. When Gemma finds out that Kartik has been in contact with, and working for, her teacher Ms. McCleethy (who is urging Gemma to give over her magic for the sisterhood she is attempting to put back together) and Fowlson (who is, in fact, working with McCleethy also), Gemma is furious and the two fall out again. Kartik denies ever having given MCleethy or Fowlson any information about Gemma, waits for her, and they make up. Kartik accompanies Gemma to the realms, where they go to the Temple and touch hands where a circle is painted in the wall, an action which is legendary to the Order and the Rakshana, who were once lovers. The action allows each to walk in the other's dreams... with the understanding that to succeed is to show them that they are destined to be lovers. They leave the Temple, and Kartik is upset at the sight of his brother's corrupted soul, and later returns to kill him, essentially freeing him. In an attempt to save Gemma's life while the power of the Tree of All Souls has taken over her, Kartik offers himself as a sacrifice in Gemma's stead. When she is released, she kisses him, glad to have been set free and thinking that they can be together again. Learning what he has done for her, she attempts to destroy the Tree to save Kartik. However, the power of the Tree enters him, and when they kiss, the Temple's magic (which resides inside of Gemma) and the Tree's magic (which now resides inside of Kartik) mingles and becomes one. He is absorbed into the tree, still kissing her, and his last words are her name. His final appearance in the novel is in Gemma's dreams, and is waving to her from the other side of the river (the afterlife), waiting for her.