Talia al Ghul (Arrowverse)

Talia al Ghul is a major antagonist of the fifth season of Arrow.

Past
Talia was pivotal in Oliver becoming a vigilante. Despite Talia training Oliver, she never gave him his full name and thus, Oliver never connected her to Ra's al Ghul.

After learning of the death of her student, Yao Fei Gulong, Talia tracked down Oliver who had information about it. Talia eventually found Oliver in Russia, prisoner of the Bratva Captain Ishmael Gregor. Talia saved Oliver from captivity and afterwards offered to train him and help him take down the corrupt official Konstantin Kovar. Together, the two raided and murdered the organization of one of Kovar's close associates, Misha Yurievich. After Misha's death, Talia convinces Oliver to track down and kill the people on "The List", a document his father gave him before his death, as these people were similar to Kovar and were polluting and corrupting Starling City. From Talia, Oliver got his green suit and hood and his bow. He was also told by her that the Hood would help him hide the monster inside him so that Oliver would not be tainted by his actions as the Hood.

Together with Oliver, Talia tracked down the drug dealer Hideo Yamane and killed him, as Yamane was a heavy influence on Star City's drug market.

Shortly after her father's death by Oliver's hands, Talia was approached by Adrian Chase, whose father was murdered by Oliver as well. Adrian sought training so that he could match the Green Arrow's powers and Talia agreed to train him as she still hated Oliver for killing Ra's.

Assisting Prometheus
Five years later, after witnessing that Prometheus, a serial killer in Star City, uses fighting techniques similar to those Talia taught him, Oliver decides that Talia has something to do with Prometheus. Oliver eventually tracks Talia down to a monastery on top of a snowy mountain. Entering it, he finds several of Talia's recruits training. When they see Oliver, they intend to kill him because as a former student, he is not welcome there. The conflict is disbanded by Talia herself, who sends her students away. Now alone with Oliver, she claims that she would apologize for her studen's enthusiasm but Oliver should not have come. She claims that their mutual business concluded five years ago but Oliver claims that this is untrue as one of her former students tried to kill him. Talia claims that the student in question does not mean to kill Oliver but that he wants to destroy Oliver utterly. Oliver realizes that Talia knew of Prometheus and accuses her.

Talia tells Oliver that Prometheus sought her out two years ago but Oliver interrupts her, angrily shouting that Talia should have warned him if she knew of Prometheus' intentions. Talia in turn reveals that she helped Prometheus in his pursuit of vengeance because he killed both Prometheus' and her own father. She reveals herself to Oliver as Talia al Ghul and Oliver realizes that she is Ras' daughter. Oliver expects no help from Talia under these circumstances but Talia claims that she will help Oliver because she wants him to suffer. She then tells Oliver that Prometheus is in truth Adrian Chase.

When Oliver later confronts and fights Oliver, the fight is ended when Talia suddenly appears and shoots Oliver with a tranquilizer arrow. She and Adrian bring the unconscious Oliver to an undisclosed location where they chain him up in a cell. When Oliver wakes up, he finds both Talia and Chase standing in front of him.

Talia sarcastically claims that she never taught Oliver to escape from shackles. Oliver replies that while Ra's was an honorable man, Talia allied himself with a psychopath and Ra's would be ashamed of her. Talia tells him that when it comes to the shame of fathers, Talia bows to Oliver's superior expertise. She then turns around and leaves, telling Adrian to make sure Oliver suffers.