|“|| Lucien: This is about station. A simple stable boy besting a tyrannical king! You have to admit, it's a hell of a story.
Klaus: I am not the villain of this fairy tale you've conjured! Lucien...we were friends.
The relationship between the Original Hybrid Niklaus Mikaelson and the Upgraded Original Vampire Lucien Castle. Klaus and Lucien's relationship began in 1002, Southern France after Lucien was found by the Original Vampires during their early days as vampires.
Lucien aided Klaus and his family by helping them assimilated into high-class society as nobles, bringing them to the castle he served. Klaus seemed to find a kinship with Lucien after he told Klaus his views on the nobles and that he wouldn't mind if Klaus and his family killed them all. Sometime after, Klaus turned Lucien into a vampire.
Centuries later, Lucien has come to New Orleans to warn Klaus of a brewing war between sirelines and to remind him of the ruthless monster he once was.
1002, Southern France
When Klaus and his siblings were fleeing through Europe, trying to escape their father, they attacked a group of finely dressed nobles in a caravan. While contemplating whether to steal their victims' clothing and pose as them so they could finally have a place to stay, they stumbled across Lucien, a servant at a nearby castle. Having heard their potential plan, Lucien promised that he could help them with their ruse, offering to teach them how to pose as noblemen. Some of the Original Vampires wanted to kill Lucien, either to protect themselves from public knowledge or just so they could eat him. However, Rebekah and Finn wanted Lucien to live, however, wanting to accept his offer and use him to get into the castle. Klaus had the final vote, choosing to let Lucien live.
Lucien brought them to the castle, having given them information on those at the castle and telling them how to properly conduct themselves. He then presented them to his master, Count de Martel. Using what they had learned from Lucien, the Original Vampires managed to fool the count and succeed in their plan, integrating themselves into his court. Klaus thanked Lucien for his service and Lucien continued to teach him about the world he had brought them into, warning him about the count's children, Tristan and Aurora and that Klaus should keep far away from them. He also voiced his disdain for the nobles he served, saying that the count was vicious and had even killed his father. He went so far as to say he wouldn't mind if Klaus and his siblings murdered everyone, much to Klaus' amusement and interest.
Throughout The Originals Series
In For the Next Millennium, while Klaus was presenting a showcase of his art, Lucien appeared, reuniting with Klaus after centuries and asking him if he'd get a drink with him. They reminisced about the past for awhile before Klaus finally questioned Lucien on what he was doing in New Orleans. Lucien revealed of a growing war between the sire lines of the Original Vampires, reminding him that if an Original died, all of the vampires in their bloodline would be killed. The threat of this had escalated into a turf war between the sires. He brought Klaus to his penthouse where he introduced him to a cypher known as Alexis. When Klaus fed on her, it revealed a prophecy of his future, one of doom for his whole family. Klaus refused to listen to it, much to Lucien's anger, telling Klaus that he was just trying to help him since he needed him to be the monster he used to be if they were to survive the sire war. He told Klaus that he was the only he could trust to which Klaus reminded him that he trusted no one.
In You Hung the Moon, after recognizing the scarred faces of two murder victims in New Orleans and that Lucien was responsible for the massacre of werewolves in the bayou, Klaus contacted him. Lucien initially denied the accusations but Klaus was quick to remind him that he'd seen the scarred faces before. Klaus also offered to speak to Lucien in person, saying he'd give Lucien his blood so he could heal from the werewolf bite he had received from Jackson Kenner but Lucien refused the offer, lying that the bite didn't sink in enough to spread its venom. Klaus then warned Lucien that if he brought chaos to New Orleans after months of peace, the next gruesome murder would be his. Later, Lucien used a syringe to pour an unknown substance into his werewolf bite, healing it.
In Out of the Easy, Klaus invited Lucien to Thanksgiving dinner along with Tristan and Aurora, to discuss what business they really had in New Orleans, now that Klaus was aware of Lucien and Tristan's secret alliance. Lucien made it clear that he never lied about wanting to protect Klaus, although instead of simply keeping watch over him, he along with Tristan, planned on sealing Klaus and his siblings away for eternity with The Serratura to ensure his own survival. Lucien also made Klaus aware that he had Cami hostage, as leverage so Klaus couldn't harm him, knowing Klaus's affections for her. After learning that Aurora had thrown Rebekah's neutralized body into the sea and the Originals capturing Tristan, Lucien handed over the Serratura to Klaus, as a show of apology and renewed loyalty. However, Klaus was furious with him when he discovered that under his watch, Aurora had kidnapped Cami.
In The Other Girl in New Orleans, Lucien tried to help Klaus find Camille but continually reminded him that she was just a normal, mortal woman and probably wasn't worth all of his efforts. Tired of listening to Lucien's judgments, Klaus snapped his neck in an alleyway to continue the search alone.
In A Ghost Along the Mississippi, Lucien rescued Aurora from her entrapment in the Mikaelson compound. Klaus deduced that it was him, knowing Lucien had access to dark objects and was the only person left who would risk their life to help Aurora.
In A Streetcar Named Desire, Lucien tried to stop Aurora when he learned she planned on killing Klaus with the newly discovered remaining white oak, since he he was still part of Klaus's sireline and would die if he did. He then offered to help the Mikaelsons in saving Klaus from the Strix's captivity, since Aya planned to test her plan to break the sirelines by executing Klaus, possibly murdering Lucien. Though the sireline was severed and Lucien's life was no longer linked to the Original, Klaus was rescued thanks in part to Lucien's efforts.
In No More Heartbreaks, Lucien kidnaps Klaus and forces him to undergo torture from Aurora. Hayley and Camille help Klaus escape though. Lucien later retaliates by biting Cami viciously, giving her a incurable, deadly bite.
In Where Nothing Stays Buried, once Klaus has the manpower and the perfect plan to do so, Klaus retaliates against Lucien for killing Cami. Freya Mikaelson is able to extracted the Beast's curse from Lucien's body and Klaus kills Lucien as revenge for killing Cami. Klaus tells Lucien that he is nothing before ripping out the vampire's heart.
- Lucien: "You are my sire. My fate is linked to yours."
- Lucien: "We are not friends!"
- Lucien: "We are as alike now as brothers."
- Klaus: "We brought out the worst in each other. In some ways, we made each other who we are."
- Lucien: "I have a vested interest in keeping you alive."
- Lucien was the first vampire ever sired by Klaus.
- Lucien and Klaus are the first sire-progeny group ever.
- Lucien is aware of Klaus' daughter.
- According to Michael Narducci, Lucien really does love Klaus and considers him his friend.
- Klaus and Lucien both loved the same woman, Aurora de Martel.
- Klaus chose to let Lucien live instead of killing him when he and his siblings found him hiding amongst their victims' bodies on the way to France.
- Klaus claimed that he and Lucien were toxic for one another.
- Lucien is no longer sired to Klaus.