|“||I have done some dreadful things, but the lies your uncle told were meant to protect you. He is a good man with a loyal heart, and he is your family.||”|
Klaus first met with Kieran when his child was in danger from a witch named Agnes, who also happened to be responsible for his nephew's suicide and massacre at his church. Klaus then made a deal with Kieran to protect his niece from danger and protected her from himself and his secrets. Afterward, the two shared a tenuous alliance until Klaus was forced to mercy-kill Kieran in An Unblinking Death.
Throughout The Originals Series
In Fruit of the Poisoned Tree, Klaus went to the Human Faction meeting at St. Anne's Church and got Kieran's attention by informing him that a witch named Agnes had hexed his nephew Sean with the Rosary of Madness, which indirectly drove him to insanity and led him to kill his entire seminary school class before committing suicide. Kieran used the Faction's resources to find her current whereabouts, though he intended to use the information for himself to get revenge rather than to help Klaus. However, Klaus ultimately talked Kieran into letting him handle it, and in return, Klaus promised to protect Kieran's niece Cami from the crossfire of the supernatural war that was brewing in New Orleans.
In Reigning Pain in New Orleans, the Human Faction moved to attack the vampires at the compound without Kieran's knowledge after Klaus refused to parley with them following his ascent to leader of the vampire clan. In retaliation, Klaus and Marcel killed all of the Human Faction members except for Kieran, who Marcel insisted they spare because of how vital a role he played in the community. Klaus ultimately agreed to spare his life, and then tasked him with rebuilding the Human Faction so they could return to negotiations. Later, upon learning that his biological father's pack had migrated to the Bayou with the other werewolves, Klaus came to Kieran at the church for his help in making sure they stayed safe. In return, Kieran asked Klaus to compel Cami to leave town for her own safety, as he had realized that the tensions between the supernatural and human factions were growing too high for comfort. Although Klaus did compel her as he had promised, Davina discovered what had been done to her and magically stripped the compulsion from her mind, giving her no obligation to leave town as Kieran wanted.
In Après Moi, Le Déluge, Esther's body was buried and consecrated on New Orleans soil by Kieran and Sophie to make Esther a New Orleans witch ancestor and give Sophie the power of an Elder so she could complete the Harvest ritual. Kieran also helped give Klaus' father's werewolf pack shelter and food at the church during the torrential rainstorms caused by Davina's out of control magic.
In Crescent City, Klaus tried to help Kieran overcome his hex by bleeding the vervain out of his system and compelling him to not succumb to his effects. However, this failed, leaving Kieran extremely agitated and frustrated.
In The Big Uneasy, Klaus asked Genevieve for help in lifting the hex that Agnes put on Kieran, but she was initially unwilling due to her jealousy regarding Klaus' affection toward Cami. However, when Cami gave Genevieve a thoughtful gift at the Feast of the Blessings celebration, Genevieve was so touched by the gesture that she briefly decided to help reverse Kieran's hex. Unfortunately, she quickly changed her mind when Klaus then offended her by killing the witch who tried to steal Esther's grimoire from the compound on Genevieve's orders. Afterward, Genevieve was so furious at him that she instead decided to do nothing and leave Kieran to suffer from the hex until it killed him as punishment for Klaus' actions.
In An Unblinking Death, Klaus rushed to Kieran's bedside after he heard that Cami was trying to alleviate his symptoms using electroshock therapy. When the shock therapy fails and Kieran's heart starts to fail, Klaus massages Kieran's heart to keep him alive a little longer. Cami begged Klaus to feed Kieran his blood to save him, even when Klaus reminded her that he would turn into a vampire, so Klaus did as she asked, and Kieran died with vampire blood in his system. When Kieran awoke in transition, Klaus explained to him what had happened to him, understanding that Kieran wouldn't want to feed to become a vampire and only intending to give Cami time to say goodbye without the hex's influence. Unfortunately, the hex ended up reemerging shortly after he reawakened, and a hallucination of the witch Bastianna convinced Kieran to feed on Cami's blood to complete his transition before killing her as his "final penance" before he was purified of his sin of interfering with the Harvest. Klaus, having realized Kieran's hex had returned, came back to the church to save Cami from dying at Kieran's hands, and with Cami's blessing, Klaus staked him to put him out of his misery. As Kieran died, Klaus confessed that he deserved much better than the outcome he was given.
In A Closer Walk With Thee, Klaus attended Kieran's funeral service to pay his respects to the priest. Afterward, he attended the wake at Rousseau's bar, where he, Hayley, and Elijah came to support Cami in her time of need.
- They both agreed that Camille needs to leave town.
- They both seem to care about Camille's health and sanity.
- In Reigning Pain in New Orleans, Kieran was the only member of the Human Faction that Klaus did not have a hand in killing.
- However, he did end up mercy-killing him episodes later in An Unblinking Death.
- When the Human Faction attacked the vampires at the compound in a drive-by shooting, killing several of Klaus and Marcel's vampire soldiers, Klaus and Marcel killed everyone in the Human Faction except for Kieran. Afterward, Klaus put Kieran in charge of rebuilding the Human Faction with new members.
- After Klaus and Kieran had formed a sort-of friendship, Klaus turned Kieran into a vampire to save his life before eventually having to mercy-kill him.