|Name||Jack Kline Née Rooney|
|Dates||May 18, 2017 (born)|
|Location||North Cove, Washington|
|Episode(s)||12.23 All Along the Watchtower|
Jack Rooney is the Nephilim son of Kelly Kline and Lucifer. He was conceived when Lucifer inhabited the body of President Jefferson Rooney, with whom Kelly was having a relationship. Angels believe that Nephilim are abominations that can destroy worlds; as Jack is the son of Lucifer, it is believed he will also be a force of great evil. However, after the Nephilim, while in utero, gives Castiel a glimpse of the future, Castiel believes Jack will bring peace and paradise to Earth.
Castiel sensed a massive surge of celestial energy and discovers that a Nephilim has come into being. Sam, Dean, and Cas realize that the Nephilim is the spawn of Lucifer. After abducting Kelly, they explain that Kelly is carrying Lucifer's child. At first, she doesn't believe them, but after she places her hand on a bible, it bursts into flames. When Castiel takes Kelly to a diner after they exorcise Lucifer from President Jefferson Rooney, Kelly tricks Cas into believing that she is going to the bathroom and escapes. She later calls Cas and tells him that she can't get rid of her baby, stating that she is its mother and it's her child before hanging up.
Cas tells Sam and Dean that he has had no luck with Lucifer's kid. At first Wally thinks this is a joke, but eventually realizes it's not.
Kelly is eating at a diner, but she doesn't realize that the waitress is an angel. After she is confronted by them, she is saved by Dagon who tells her that she can protect her and her child. She states that nothing is born evil and that "he could save us all," confirming the baby's gender in the process.
Mick, after learning that Sam and Dean knew about the Nephilim, tells them about how dangerous the child will become if it is born. Dr. Hess later tells Mick that the situation concerning the Nephilim has become more important than their current plan to recruit American Hunters.
Kelly, after experiencing some pain, demands that Dagon takes her to a doctor. He performs an ultrasound of the baby; he notices something unusual, but Dagon telepathically instructs the doctor to tell her that "everything looks a-okay." After Dean takes Kelly and tries to convince her that she can't have the baby, she tells them that she loves the child and refuses to get rid of it. When Dagon appears to take her away, she willingly goes with her. Later, Dagon chains Kelly to a bed and tells her that she cannot be trusted. Kelly tries to explain that she was worried about the baby, but Dagon bluntly tells Kelly that the baby will be just fine and that birthing a Nephilim is always fatal for the mother.
After spending a few days refusing to eat, drink, or bathe, Dagon forces Kelly to take her pills and tells her that her son will be born and bring an end to all no matter what happens to her, and that she should take a bath. Kelly tries to kill herself because she can't let what Dagon says happen to the world, despite her love for her child. After she dies, the Nephilim revives her. Dagon eventually discovers what happened and tries to explain the baby saving her as an act to save himself and reminds Kelly that she will die when he is born. After this, Kelly is influenced by the powers of the Nephilim and believes that her son is not evil and will bring paradise to the world. After Joshua tracks a disturbance caused when the Nephilim revived Kelly, Castiel, Kelvin, and Hozai are able to track Dagon down. After Hozai is killed and Kelvin is captured, Cas escapes with Kelly.
After exhausting the information they have on Nephilim, Sam is able to determine that it will be born on May 18. He realizes that the Grace Extractor could render the Nephilim human so that Kelly and her baby wouldn't have to die.
After communicating with Joshua, Cas tries to bring Kelly to Heaven's Gate. Kelly tries to convince Cas to let her baby be born, believing that it could lift the world to its feet rather than bring it to its knees. She explains how she tried to kill herself and how the baby was able to bring her back, but Cas believes that her revival was not proof of goodness and he asks who will keep the baby on the righteous path when she is gone. Kelly asks him if he wants to feel the baby kick, but when Cas puts his hand on her belly, he experiences a vision introduced by the Nephilim.
Sam and Dean are able to catch up to them and explain that they have a plan to render the baby human with the Grace Extractor, but Kelly refuses to let them do it since she wants her baby to be born with all its powers. While waiting in the Impala for Sam and Dean, Kelly takes the keys and drives away from the motel, believing that Cas will be able to take care of her baby when she is gone.
After arriving at Heaven's Gate, Joshua appears and tries to tell Kelly not to be afraid, but Dagon appears and kills him. She reveals that Kelvin told her where they would go after they escaped. After Sam and Dean catch up, they try to keep Dagon away from Kelly, but she gets the better of them and goes after Kelly. Kelly holds Castiel's hand; through this connection the Nephilim transfers its power to Cas temporarily and allows him to incinerate Dagon, killing her. Cas, influenced by the Nephilim's power, decides to leave with Kelly to allow her child to be born. When Sam and Dean try to stop them, Cas knocks them out and they drive away in his truck. Cas tells Kelly that the Nephilim showed him the future.
Dean talks to Sam about how the Nephilim was able to mess with Castiel's mind, despite not being born yet.
Cas and Kelly prepare for the Nephilim to be born by renting a house in North Cove, Washington, purchasing a truckload of diapers, and preparing its room. Kelly even gives him a name: Jack. She makes a video for Jack to watch after she dies, telling him how much she loves him. When she feels a contraction, she unknowingly releases a bit of the Nephilim's energy, which makes a rift to an Alternate Universe. After Sam, Dean, Mary, and Crowley arrive, they discover the rift made by the baby's energy. Mary tries to help Kelly as she goed into labor while Sam, Dean, Cas, and Crowley try to use the rift to imprison Lucifer.
While they deal with Lucifer, Kelly Kline finally gives birth to Jack in an explosion of light that renders Mary unconscious. When Sam notices the light coming from the home, he goes to check on Kelly, only to find her lying dead in her bed. He hears a noise, and goes to investigate. He sees footprints scorched into the floor leading to Jack's nursery, where he finds an already adult-looking Jack huddled in the corner, smiling sinisterly as his eyes glow gold.