Arrow, the show that spawned The CW's sprawling DC shared universe, is now in its fifth season and closing in on its 100th episode. Oliver Queen a.k.a. The Hood a.k.a. The Arrow a.k.a. The Green Arrow has been through a lot of adventures across those episodes, both in the present day and in the series' ongoing flashbacks, and some of his most notable adventures have involved the al Ghul family.
Already Arrow fans have gotten to know Ra's al Ghul (Matt Nable) and Nyssa al Ghul (Katrina Law) very well, but now another member of the infamous family is set to join Arrow in season 5. CBR reports that Lexa Doig (Continuum) has been cast in a recurring role as Talia al Ghul, Nyssa's half-sister, and will make her first appearance in season 5, episode 10, "Who Are You?" According to The CW's official description of her character, Talia is "an elite warrior who doesn’t pick sides but rather creates her own."
Talia al Ghul has already appeared in the Arrowverse, though not in Arrow; a season 1 episode of Legends of Tomorrow, "Left Behind," featured Talia as a child (played by Milli Wilkinson), and also saw Nable reprise his role as Ra's al Ghul. The most famous on-screen portrayal of Talia al Ghul to date is in Christopher Nolan's The Dark Knight Rises, where the character was portrayed by Marion Cotillard.
Speaking in an interview last year, Arrow's executive producer Andrew Kreisberg said that he and the other showrunners were happy focusing on Nyssa's story arc, and that "if we ever think of a reason to have a Talia or whatever incarnation we decide to do, it would be in service of furthering Katrina's story." This means that the arrival of Talia al Ghul could also signal Nyssa al Ghul's imminent return to the show (Law hasn't guest-starred since season 4).
A recent report claimed that neither Talia al Ghul nor her father are set to appear in any of Warner Bros.' currently planned DC movies, so fans of the character who don't already watch Arrow should consider doing so for this season, since it will be the only place to find a live-action take on Talia for the foreseeable future. The character has been around in the comics since 1971, where she has been romantically involved with Batman and also has a child with him, Damian Wayne, who eventually took up the mantle of Robin.
Arrow's next episode, ‘Human Target’ airs Wednesday @8pm on The CW.