Holland Roden as Lydia Martin -Banshee-
Lydia Martin is Beacon Hills High’s most popular female student, a member of Scott’s Pack, the former love interest of both Jackson Whittemore and Aiden, she was Allison Argent’s best friend, and (revealed in Season 3 episode “The Girl Who Knew Too Much”) is a banshee. In Season 1, Lydia at first appears to be the archetypal promiscuous high school queen bee. In reality she is surprisingly caring to her friends, befriending Allison on her first day at school. Lydia is also extremely intelligent, having a GPA exceeding 5.0. Her love interest is Jackson Whittemore, although she initially makes it apparent she is merely dating him due to his high social status as the school’s lacrosse team captain, she is actually in love with him. At the start of the series, Lydia gives the impression of barely knowing who Scott and Stiles are, only expressing interest in Scott after he is Bitten and shows skill at lacrosse. Stiles, throughout Seasons 1 and 2, has an intense, sweet crush on Lydia, but she does not reciprocate. In the Season 1 penultimate episode “Formality”, Lydia is Bitten by the Alpha werewolf Peter Hale but neither dies nor turns. Instead, she is later revealed to be immune.
In the beginning of Season 2, Lydia recovers, but suffers from a hallucination while in the shower and goes into a fugue state running around in the woods naked for two days. Later she doesn’t remember the entire experience at all. Lydia is determined to be immune to the Kanima’s venom, and thus Derek assumes Lydia is the Kanima, although it is later revealed to be Jackson. Lydia suffers further fugue episodes and hallucinations throughout the season which, along with Jackson’s rejection, causes her to have emotional breakdowns. The hallucinations are caused by Peter, who planted an imprint of himself in Lydia’s mind with his Biting her, possessing her to use her to return to life. As a result, she learns pieces of the supernatural events that were happening. In the Season 2 finale, Lydia selflessly faces the Kanima and successfully coaxes him to transform back into Jackson, by holding up the house key Jackson had given her when they were together. When Jackson asks if she still loves him while he’s dying, she responds that she does and embraces him when he is cured of being a Kanima and resurrected as a werewolf.
By Season 3, Lydia has been brought up to speed on the supernatural, has greatly matured and is closer to Scott and Stiles. She and Jackson have parted since he moved to London and she is attempting to get over it. Lydia enters into a purely physical relationship with Aidan, initially to distract herself from Jackson, unaware he was assigned to get close to her to get leverage on Scott. Lydia displays a strange connection to the events occurring in Beacon Hills being mysteriously drawn to the locations of several of the sacrifices and occupying her time with drawing the same tree over and over again. Lydia joins forces with Stiles to figure out who is really behind the sacrifices. In “The Girl Who Knew Too Much”, Cora Hale tells her all Scott and Stiles do is find bodies, not save anyone. Lydia later appears at the memorial recital with the decision to stop fighting her strange connections to the murder sites if it could help save someone and Scott gives her his support. Later she is held captive by Jennifer Blake, the Darach, who attempts to kill her and Lydia lets out a high pitched Scream. Jennifer then reveals to Lydia that Lydia’s supernatural status is she is actually a banshee, the Wailing Woman. Lydia and Stiles find out the tree she’s been consistently drawing is an inversion of the Nemeton’s root system, which allows them to realize it’s where the kidnapped parents are being held. During Season 3B, though Lydia continues her liaison with Aiden, she eventually tells the werewolf that he is only a ‘bad guy’ because he helped to kill Boyd, while she uses her abilities to help save lives. Lydia’s talents allow for her to listen to or communicate on a network that predicts death: Jeff Davis has revealed this network is the whispers of other banshees. The Nogitsune kidnaps Lydia in “Insatiable” and takes her to Camp Oak Creek. She senses the pending death of the Nogitsune – only this was the reason the Nogitsune took her, to know in advance when the Oni would appear to kill him, so he would be able to take control of the demons. Lydia had warned the others through a message relayed by fellow banshee Meredith Walker not to come for her, because she had sensed an impending death – Allison’s. Lydia Screams for Allison when she’s impaled by an Oni and is overcome with grief as she “feels” her best friend’s death. In the Season 3 finale, Lydia meets Deaton with Scott, and comes up with the idea to use the triskele urn which held Talia’s claws to trap the Void kitsune. Shortly after the Nogitsune’s defeat, she “feels” another death – this time it is Aiden. Despite her previous opinion of her lover being a ‘bad guy’, she grieves his death from fighting the Oni as a ‘good guy’.
In Season 4, Lydia has started over with close friends in Kira and Malia. Lydia helps Malia in her schoolwork by lending her notes. She learns some notes she’s lent are actually computer code she doesn’t remember transcribing, courtesy of her banshee talents. Lydia’s family owns a lakehouse previously owned by her paternal grandmother Lorraine Martin, who’d supposedly committed suicide. Lydia finds a soundproof study at the lakehouse where she hears “the whispers”, learning the computer code comprises the Dead Pool, the hit list of supernaturals in Beacon Hills as well as the first cipher key to decode the list: ALLISON. Lydia immediately works on getting the other two cypher keys, later learning from Meredith the second is AIDEN. Lydia cracks the final third of the Dead Pool but sees that Meredith is on the list. She is saddened that Meredith, “the only other banshee (she)’s ever known,” has supposedly committed suicide out of fear. Lydia later learns her grandmother Lorraine was also a banshee; she’d written a list of names, part of the Dead Pool code which lead her and Stiles to Eichen House. Lydia learns Lorraine was actually murdered by Brunski, and that Meredith is alive and has been ‘the Benefactor’ all along. At the sheriff’s station, Lydia learns of Meredith’s history with Peter and Meredith reveals to Lydia she’d enacted the Dead Pool after ‘hearing’ Lydia’s Scream when she felt Allison’s death, because of how many people have died because of the supernatural. Lydia truthfully tells her, “Not all monsters do monstrous things”, which Meredith realizes to be true, the two banshees coming to an understanding. At the conclusion of Season 4, Lydia gives Parrish a hard copy of the bestiary and offers to help him identify what supernatural species he is.