Hayley Marshall-Kenner/Throughout The Vampire Diaries

=== Season Four ===
Hayley sets off to find Tyler when she hears from one of Klaus' hybrids, who was from a pack she used to run with, talking about protecting him, She surprises Tyler when she shows up at his house unannounced, something which Tyler is clearly happy about. While they talk, Hayley mentions helping Tyler break his sire bond. She chastises him for lying about his real identity; apparently he had told her he lived in a trailer park in Florida. Hayley seems annoyed by this, but quickly forgives him.
When Caroline shows up and Tyler leaves the room to talk to her, Hayley meets Klaus who appears to talk to her. Klaus overhears Tyler and Caroline's conversation and Tyler makes an excuse about staying home, not mentioning Hayley. Klaus assumes that Tyler and Hayley had a fling, which Hayley does not deny. When Tyler comes back, he finds Hayley has gone and Klaus tells him she left. Klaus then speculates that Tyler and Hayley may have hooked up, although that hasn't been confirmed. Tyler only let Klaus believe something happened between them to distract him from Tyler's plan to break the sire bonds of the other hybrids.
Hayley eavesdrops on a conversation between Tyler and Dean when Caroline shows up and meets Hayley. Hayley tells Caroline she's been staying with Tyler since she needs a place to stay, and that they're good friends. Caroline is clearly irritated that a strange girl is staying in her boyfriend's house when she knew nothing about it, but Hayley doesn't seem bothered by Caroline's irritation. Hayley excuses herself to join Tyler and Dean's argument about whether Dean should obey Klaus' order to deal with Connor or not. After Dean's death, Tyler comforts Hayley which again, irritates Caroline. Tyler later explains that he and Hayley plan to help all of Klaus's hybrids break the sire bond.
Tyler finds Hayley, Chris and some other hybrids drinking in honor of Dean. Hayley keeps up the ruse that there is something romantic going on between her and Tyler by sensually wiping alcohol from Tyler's lip, knowing Klaus is witnessing it. Soon after, Caroline arrives and stages a breakup with Tyler in front of Klaus, after which he leaves with the hybrids. Once Klaus is gone, Hayley, Tyler and Caroline smile at one another, and Caroline thanks Hayley for telling her that Klaus was there. Hayley watches Tyler and Caroline kiss, smiling slightly. Later, Tyler tells Stefan about Hayley and that she helped him and Chris break their sire bonds, also revealing that they plan on unsiring all the hybrids from Klaus.
That night, when Chris is about to leave Tyler's house, Klaus appears and berates Chris for failing to keep Elena secured. Tyler tries to cover for him, but Hayley intervenes to claim that she let Elena out and stands up to Klaus, daring him to kill her instead. Klaus apparently lets Chris go, but when Jeremy and Stefan arrive Klaus allows Jeremy to chop off Chris' head while Hayley and Tyler watch in horror. After Chris's death, Hayley is passed out the next morning next to Tyler on a sofa; they had clearly spent the entire night drinking in honor of Chris. After Caroline and Tyler argue she is abruptly awakened when Tyler throws a glass bottle and it explodes against the wall.
Hayley is in an abandoned barn helping Kimberley break her sire bond when Tyler arrives, saying Caroline got them another day by agreeing to go with Klaus to the Miss Mystic Falls Pageant. Hayley suggests that they go to keep up the ruse that she is the reason Caroline and Tyler broke up, and Tyler reluctantly agrees. Caroline and Klaus see Hayley and Tyler arrive, which seems to upset Caroline. Hayley mocks the pageant by donning the tiara intended for the winner. Later, Damon and Tyler see Hayley talking to Shane and Damon wonders aloud how he knows her. Tyler assures him she doesn't, but Damon's suspicion seems to plant doubt in Tyler's mind.
Later, when Tyler is sitting with Hayley, she asks if he got the wolf gene from his mother, claiming his mother knows how to party as she is seen drinking a lot and doesn't appear too drunk. He tells her he got the gene from his dad and asks her about her parents. She tells him she never knew her real parents and that she triggered the gene by accidentally killing someone in a boating accident while she was drunk. Tyler subtly asks if she knows Shane, but she claims she doesn't.
Later that night, after Tyler calls Hayley to tell her that Kimberley broke the sire bond, Hayley is in Shane's office and tells him they freed another one. She emphasizes that she doesn't want Tyler to have anything to do with whatever they are planning.
When Hayley is helping Adrian break the sire bond, Kimberley interferes and frees him before they finish. Later, she breaks into Shane's office, and when he arrives she reveals that her deal with Shane was to get him twelve hybrids, unsired from Klaus, in exchange for information about her parents. Shane threatens to include Tyler in the twelve if she doesn't manage to break Adrian's sire bond so Hayley encourages Tyler to take the role of Alpha and give Adrian orders to go through with it. He follows her advice, but Kimberley retaliates by kidnapping and torturing Caroline. Later, after Tyler has forced the hybrids to submit to him and Adrian has finally broken his sire bond, Hayley reports to Shane that they have their twelve hybrids. In return, Shane gives her a flash drive with information about her parents, informing her that they are dead but reassuring her that she can see them again. He cryptically tells her that its far from over and that they are just the beginning.
During the Winter Wonderland charity event, Tyler tells Caroline that Hayley has found a powerful witch who can use a spell to transport Klaus into someone else's body. When he reveals that he has volunteered to house Klaus's essence and be buried in concrete, Caroline, after much tension with Tyler and the hybrids, eventually has the idea that they should use Rebekah's body instead. Worried about changing the plan, Hayley texts Shane about having problems, but he merely tells her to fix it. Hayley then snaps Caroline's neck, and tells Klaus about Tyler's plan. While Klaus is killing Tyler's pack, Hayley explains to Tyler that she made a deal with someone who can help her find her real family, and that her end of the bargain was to provide twelve unsired hybrids for the sacrifice. She warns Tyler that he should leave town to escape Klaus's wrath. She then flees herself.
Hayley's whereabouts were unknown until Vaughn, a hunter, reveals to Damon and Rebekah that Katherine got her information about Silas from Hayley when they crossed paths in New Orleans.
In Bring It On, Hayley is attacked by a vampire named Will who was sent by Katherine to kill her. Klaus appears and saves her, in the process biting and poisoning the vampire with his werewolf venom. Klaus then takes Hayley to his mansion, where he plays the hospitable host in order to glean information about Katherine. He politely interrogates Hayley, though she claims she does not know where Katherine is. She tells Klaus that Katherine found her in New Orleans when she was trying to find her real parents and Katherine told Hayley she could help her. Klaus claims that he is the only one who can protect Hayley from Katherine's minions, and says that he will as long as she co-operates with him.
Hayley goes into the next room and looks at Klaus' paintings, expressing distaste for all but one, which she describes as twisted. She asks Klaus why he paints and in response he describes painting as a metaphor for control. Hayley calls him out on his attempts to soften her up before mentioning Klaus' plans to kill Tyler. Klaus assures her that the better punishment is sentencing Tyler to a lifetime of paranoia and fear. Hayley then reveals to Klaus that the reason he has been unable to find Katherine all these centuries has been her ability to build and maintain a network of allies willing to do anything for her. Klaus asks Hayley if she knows any of Katherine's allies, and she responds teasingly that she might know a couple and she might even tell him about them. Later, after Damon has killed Will, Klaus offers to let Hayley stay anyway. She suggests a deal: her intel in exchange for Tyler's freedom, but Klaus cannot bring himself to make any promises when it comes to Tyler. Hayley draws him back in by returning to what he said about his paintings and control, and tacitly offers him control with her. He takes the bait and they have sex. Afterwards, while Hayley is dressing, Klaus notices a mark on Hayley's back which, according to him, is only found on those of a certain bloodline of werewolves originating in Louisiana.
In The Originals, Hayley leaves Mystic Falls. Katherine tells Stefan and Damon that thanks to Hayley, she was what they needed to rid Klaus from their lives for good. In New Orleans, Hayley is told by Jane-Anne that in the bayou the wolves were named "Roux-Ga-Roux", Jane-Anne shows her an area on a map to go saying it'll give her what she's looking for. Hayley heads towards the area while Jane-Anne and Sophie prepare to do a spell on her. While Jane-Anne does the spell, Hayley's car acts up and weird things happen to her, when seeing other people come to her she passes out with Sophie and the other witches of the Quarter circling her. Later it is revealed by Elijah and Sophie that she is pregnant with Klaus' child.