Adelaide Kane as Cora Hale -Werewolf-
Cora Hale is Laura and Derek’s younger sister and also a born werewolf. She unknowingly survived the Hale House fire and was apparently unaware her siblings Laura and Derek were away at school at the time. Cora was long believed by Derek and Laura to be dead. After the fire, Cora ventured to South America where she lived during the intervening years. She believed her entire family was dead, but she came into town after hearing rumors an Alpha werewolf was building a Pack back in Beacon Hills, California, “one of the Hales”. After Boyd and Erica were captured by the Alpha Pack, Cora was captured also and learned her brother Derek was alive. All three were held captive in the abandoned Beacon Hills First National Bank. During this period, Erica tried to fight back, but was killed by the Alpha werewolf Kali.
Cora became friends with Boyd during their imprisonment, but the hecatolite lined in the bank vault refracted the moonlight, refraining the two werewolves from fully transforming during the full moons, causing their rage and bloodlust to build up inside. Three months later, upon being found by Derek and Scott, Cora and Boyd lost all control of their animal sides and escaped into the woods to kill. They were later subdued by Derek, with assistance from Scott, Isaac and Chris Argent. Eventually the sun rises and she and Boyd are rescued and Cora is reunited with her brother joining his Pack. Cora is impulsive, trigger-happy, short tempered, vengeful and tomboyish but she cares for those close to her. Like her older brother Derek, she gives death threats to people; of course, like her older brother, she has no intention of going through with them. In “Currents”, when Deaton is kidnapped to be sacrificed by the Darach, Cora helps Scott’s friends to find him deducing that Deaton is being held in the same bank she was locked in for three months, but she learns the Alphas have attacked Derek’s loft and sabotaged the trap for them. Cora leaves with Stiles and Lydia to help her brother. After Boyd is killed by the Alphas, she breaks down in tears and cradles her close friend’s body. Cora tries to avenge his death by killing Aiden, but fails to do so and is knocked out when Aiden strikes her in the head with a weight. She is saved by Scott and Ethan when they restrain Aiden. Her wound from the blow to her head Aiden gave her suddenly doesn’t heal, she falls unconscious and is put in the hospital. She was later revealed to have also been poisoned by Jennifer with mistletoe for leverage against Derek. Derek saves her life by giving up his Alpha werewolf status using his pain transference to heal her. In the mid-season 3 finale, Cora helps Lydia and Deaton save the lives of Aiden and Ethan after their defection from the Alpha Pack. She later leaves Beacon Hills with Derek for her former residence in South America.
During Season 3B, Cora goes into hiding at Derek’s request, remaining in South America as he undertakes a mission to retrieve their mother Talia’s claws from the Calavera hunters and they separate.