I hear Elijah has refused you the cure, and in return, you have refused my freedom. Shame on you both. But while you boys sort out your problems, I have one last thing to offer you. I have caught wind that there is a witch in New Orleans named Jane-Anne Deveraux plotting a move against you. Hunt her down. What she has to say will rattle you so deeply to your core that chasing little old me will be the least of your concerns. It's been a fun five centuries, Klaus, but I've worn down too many good heels running from you.
Love and hate,
The antagonistic relationship between the Original Hybrid Niklaus Mikaelson and the cured vampire/ witch doppelgänger Katherine Pierce. In the beginning Klaus was kind to her, but later, when Katherine discovered that he needed her for the sacrifice, she ran away. She killed herself with Rose's blood in her system, and when she awoke, she fed on Rose's housemate in order to become a vampire. Once Katherine turned, her blood became useless to Klaus, as he needed the blood of a human doppelgänger. Klaus' revenge was to kill Katherine's whole family.
They met in 1492, after Katerina (Katherine) was disowned by her family for having a child out of wedlock, and exiled from her home in Bulgaria. She immigrated to England, where she eventually met Elijah and Klaus, who at the time were noblemen. She became friends with them for a short time, but as soon as she found out their intentions with her, she ran away, and took the moonstone with her. She then became a vampire after she tricked Rose into feeding her her blood. Later, Klaus found her village in Bulgaria where she was born, and slaughtered her whole family as punishment for thwarting his plans.
Throughout The Vampire Diaries Series
Klaus had compelled Isobel to get Katherine to go to his warlock Maddox and take Katherine for him. He reveals himself to Katherine in Know Thy Enemy. In The Last Dance, Klaus—who still was in Alaric's body—gets information on Elena and her friends. He then compels Katherine to hurt herself by sticking a knife in her leg and repeating it again and again. Later on, he asks her for her opinion on what shirt to wear to the dance, he gets surprised by the many weapons found in Alaric's Apartment and asks her who Alaric is. In Klaus, it is shown how Katherine and Klaus met in 1491. Damon gets some Vervain for her, so she can stop being compelled by Klaus. In The Last Day, Damon asks Katherine where Klaus has kept Caroline and Tyler. She replies by giving him the address. Klaus returns to Alaric's Apartment and is immediately suspicious of Katherine. He compels her to tell him what she has been doing, but as she is taking vervain, she is able to lie. He is still suspicious and 'compels' her to take off her bracelet, walk to the window and stand in the sunlight. Katherine has to do it and screams. Eventually, Klaus believes she is compelled and says she needs to do something for him. Klaus later compels Katherine to phone Jenna so he could get his vampire for the sacrifice. In As I Lay Dying, Klaus bites Katherine, so he can show Stefan the cure to a werewolf bite. After Stefan gives in to Klaus plan, the hybrid tells Kat to bring Damon the cure, because he will die soon of a werewolf bite. Katherine runs away fastly, because she drank vervain, and can't be compelled anymore, not even by the powerful Klaus. Despite this fact, Katherine gives Damon the cure and runs away from Mystic Falls to hide from Klaus.
In Disturbing Behavior, Katherine shows up near Klaus and Stefan. She talks with Stefan about teaming up with him to find a way to kill Klaus, but Stefan refuses. So Katherine decides to create a new plan and makes a road trip with Damon to free a very old vampire named Mikael, who claims that he can kill Klaus. They will later learn that Mikael is Klaus' stepfather. In Homecoming, Katherine pretends that she's Elena and meets Klaus at a party at Tyler's house. They talk and it's obvious that Katherine is pretty nervous. Klaus is being flirty in the beginning, which turns into a warning that they can try to kill them, but eventually, it won't work. In the end, the plan fails like Klaus predicted. Katherine encourages the now freed Stefan to start his own revenge on Klaus. After that, Katherine disappears again.
The race to get the cure to end the status of vampirism is over when Katherine makes a surprise appearance and is force-fed the cure by Elena. Soon after Klaus finds that out and wants to find her even more than ever. He thinks that she will force him to take the cure, so that he's vulnerable and can be finally killed. In reality, Katherine wants to negotiate with Klaus to regain her freedom: She will give him for her liberty the cure, so that he can do with it whatever he wants. For this negotiation, she needs Elijah, who turns away from her and refuses to give the cure to Klaus. Consequently, Klaus refuses Katherine her freedom, who afterwards sends Klaus a special letter:
"...while you boys sort out your problems, I have one last thing to offer you. I've caught wind, that there's a witch in New Orleans called Jane-Anne Deveraux plotting a move against you. Hunt her down. What she has to say will rattle you so deeply to your core that chasing little old me will be the least of your concerns. It's been fun five centuries, Klaus, but I've worn down too much good heels running from you. Love and hate,
As Klaus was in New Orleans, Katherine has a talk with Rebekah, in which she admits, that Klaus and she are the same: "We manipulate, we thirst for power, we control, we punish, but our actions are driven by one singular place deep inside: We're alone... and we hate it."
Klaus returned to Mystic Falls as he was informed by Damon that Katherine is dying. However, Caroline Forbes deterred him from his initial plans to watch and gloat as she died.
- Katherine: "It's a long story, Klaus and I. It goes all the way back to England, 1492, after I left Bulgaria. Or was thrown out."
- Elena: "Thrown out?"
- Katherine: "My family, your true ancestors, they disowned me. My indiscretions were not tolerated at that time. I had a baby out of wedlock. The shame."
- Elena: "It was kept secret?"
- Katherine: "Mm-hm. My baby was given away. I was banished to England and I had to learn to adjust. So I quickly became English. It was there that I caught the eye of a nobleman named Klaus. I was taken with him at first, til I found out what he was and what he wanted from me. And then I ran like hell."
- -- Katerina
- Katherine was the next doppelgänger after Tatia; a woman whom Klaus was in love with and who was identical to Katherine.
- Katherine "was taken" with Klaus at first when she had been human.
- Katherine had been the object of Klaus' hatred for over five hundred years after she turned herself to evade his plans.
- In revenge for ruining his plans, Klaus slaughtered Katherine's entire family.
- Katherine ran for over five hundred years from Klaus.
- In The Kindness of Strangers, (an episode of The Originals series) a flashback of Hayley and Klaus is shown and they are trying to figure out what name to give their then-newborn daughter. When Hayley suggests the name “Katherine,” Klaus responds with, “god no,” which implied that he may have been thinking about Katherine Pierce.