Possession

Possession is the ability of witches, passengers, spirits,ghosts, and oni to insert one's spirit into another being's form and take control of their body and mind. This power can be used to grant the possessor the motor functions, senses and supernatural abilities, if any, of the host body and is commonly achieved through magical means; however, oni can achieve this through mere touch.

Possession is different from Mind Compulsion and mind control, in that the being's spirit or life essence has to metaphysically enter the body of another being in order to control the body from within.

Emily Bennett
In History Repeating, the spirit of the long-deceased witch Emily Bennett possessed the body of her descendant, Bonnie Bennett while she was performing a séance with Elena Gilbert and Caroline Forbes with the intention of using Bonnie's body and magic to destroy the Bennett Talisman before Damon Salvatore could find it and use it to release the tomb vampires.

Emily later possessed Bonnie again in As I Lay Dying, when Stefan and Bonnie called upon the spirits to beg them for a cure for Damon's werewolf bite. She insisted that it was Damon's time to die, and refused to give them any answers about the cure. When she painfully exited Bonnie's body, angry that Bonnie continued to abuse the spirits' power, Bonnie managed to hear the spirits say that Klaus had the cure, which was ultimately revealed to be in his blood.

Niklaus Mikaelson
Klaus began possessing Alaric Saltzman's body for a short time at the end of Know Thy Enemy, as a way to get close to Elena Gilbert. Once he learned that Bonnie had regained her powers, he decided to kill Bonnie; however, he struggled with a way to go about it, as he knew she had just performed the spell to connect her to the large source of magic at the Witch Burial Ground, and would thus be extremely powerful. Klaus incorrectly assumed that Bonnie wouldn't be willing to hurt or kill Alaric, but Bonnie continued to attack him knowing that Alaric would have wanted her to make him suffer. Unbeknownst to Klaus, Bonnie already had a plan and faked her own death in order to lull Klaus into a false sense of security. Shortly afterwards, Klaus left Alaric's body to be put back into his own in Klaus, because he claimed he was too vulnerable in Alaric's human body.

In The Departed, Klaus was revealed to be possessing Tyler Lockwood's body, as a result of Bonnie's body-swap spell. Bonnie knew that Alaric, who had just been turned into an Enhanced Original Vampire, would want to kill Klaus, so she cast the spell to put Klaus in Tyler's body in order to ensure that all of her loved ones who were sired from his bloodline, such as her mother, Tyler, Caroline, Stefan, and Damon, would remain safe even if Klaus' body was destroyed.

Esther Mikaelson
In Heart of Darkness, Esther lied to Rebekah and told her that she was dying because the Bennett bloodline, which she had been drawing on for power, was broken by Abby's death and subsequent transition into a vampire. Esther began to shake, as if she were dying, and she grabbed Rebekah's hands before falling to the floor. Later, Esther revealed to Alaric's alter personality that she had actually jumped into Rebekah's body, and needed his help to kill the her children once and for all. She stayed in Rebekah's body until the next episode, where she returns to her own in order to perform the spell that turned Alaric into an Enhanced Original.

In From a Cradle to a Grave, it was insinuated that Esther has taken possession of Cassie, who was a Harvest girl and who was also the last of the four girls to be resurrected due to Genevieve's death. This was confirmed in Rebirth, as well as the fact that she had brought her sons Finn and Kol back to the world of the living as well, who were possessing two witches named Vincent Griffith and Kaleb Westphall, respectively. In Every Mother's Son, Esther vacated Cassie's body in favor of possessing another very powerful witch named Lenore, who was an ally of Marcel and who had helped Elijah, Klaus and Hayley by performing a soul-branding spell on Esther so they could keep track of the bodies she was possessing.



Céleste Dubois
In Crescent City, Céleste Dubois was revealed to have used a spell to possess numerous female French Quarter witches over the centuries to achieve a form of immortality after her physical body was killed in 1824 in a witch massacre orchestrated by Niklaus Mikaelson. Every time she got tired of the body she inhabited, or the body was no longer useful to her plans, she would jump from the bridge in the Mississippi River at the very place where she first kissed her former love, Elijah Mikaelson, killing her host body and allowing her spirit to jump into a new one. This cycle continued for almost three hundred years until she was ultimately bound to her original body by Monique Deveraux. Once she had returned to her original body, she was killed by Elijah in retribution for tormenting his family.

Gregor
Gregor was a Traveler who was seen to possess Matt Donovan's body in I Know What You Did Last Summer by using a Passenger spell commonly used by the Travelers. He continued to possess Matt's body until Dead Man on Campus, when Katherine killed him using Gregor's knife. However, the Passenger spell he used only allowed him temporary control over Matt's body, as opposed to the full control afforded to regular witches who used a body-swap or possession spell or Passengers who had sacrificed their own bodies to achieve full control with Traveler magic.

Katherine Pierce
After Nadia, Katherine's daughter, learned that Katherine was dying of old age after being cured of her vampirism, she offered to allow Katherine to take advantage of her Traveler heritage and use the Passenger spell to possess her own body. Katherine refused at first, both because she had always been told by her father that Traveler Magic was the devil's magic, and because she didn't want to take her daughter's life in order to extend her own. However, in 500 Years of Solitude, after she had temporarily died and realized she didn't want to die just yet, she ultimately performed the Passenger spell on an unsuspecting Elena Gilbert, who was both her doppelgänger and a vampire, much to Katherine's delight. Unfortunately for Katherine, Elena's strength of will resulted in Katherine frequently losing control of her body. This led Katherine and Nadia to seek out a Traveler, Mia, who made the possession permanent in The Devil Inside. While Katherine was able to successfully possess Elena's body without suspicion for quite a while, Stefan and Caroline eventually figured out that Elena was being possessed by Katherine in No Exit, and Stefan subsequently killed Katherine's spirit for good by stabbing her with the Traveler knife in Gone Girl.

Julian
Julian was a Traveler who performed the Passenger spell on an unsuspecting Tyler Lockwood in Resident Evil, after Tyler had stabbed Sheriff Forbes with Gregor's knife to expel the Passenger inside her. Julian later remarked how much he enjoyed how powerful Tyler's body was as a hybrid, but Markos, the Travelers' leader, reminded him not to get used to it, since their plan involved them all returning to their original bodies after the Traveler's Curse was broken. In Man on Fire, Tyler managed to temporarily gain control over his body at several different points in the day, which allowed him to learn important information about what the Travelers were planning. Markos used Tyler's blood to turn Sloan into a vampire as part of an experiment to test the abilities of Stefan and Elena's mixed doppelgänger blood. Once Sloan awakened in transition, she was fed the doppelgänger blood, which removed the vampire magic from and returned her to her mortal form, before she reverted back to the state in which she was killed by Markos to become a vampire—dead with a slit throat. This revealed that the doppelgänger blood removed witch magic, including the spells used to create vampires, to trigger werewolf curses, to create the Other Side, and even to enchant daylight rings.

The next morning, in What Lies Beneath, Tyler woke up at the Traveler's camp, once again temporarily in control of his body, and pretended to be Julian around Julian's wife, Maria, as to not arouse suspicion. Just as she realized that Tyler had regained control, he shifted into his wolf form, which prevented Maria from being able to command Julian forth. This allowed Tyler to escape and return to the Salvatore Boarding House to inform the gang about the Traveler's plans. While the rest of the gang left for Caroline's dad's cabin to hide the doppelgängers, Tyler stayed behind with Jeremy and Matt, who reluctantly chained Tyler up (at Tyler's insistence) in order to torture Julian into giving them answers. Matt, having remembered how to summon a Passenger from hanging out with Nadia, was able to call Julian forth. At the camp, Markos was so angry at Maria for allowing Julian/Tyler get away that he forced her to perform the spell to make Julian's possession permanent, which involved burning his original body.

In Promised Land Julian, knowing that Markos was essentially sentencing him to death, since he was now permanently possessing a hybrid whose vampirism would be stripped away by the spell, reluctantly helped Damon in his plan to thwart Markos' plan. Maria also joined the gang against Markos and the rest of the Travelers, in support of Julian, and helped the doppelgängers escape from Markos after being nearly bled dry, which ultimately led to her death at Liv and Luke's hands. When Julian learned that Maria had died protecting the doppelgängers, he became so enraged that he killed Stefan by ripping his heart out. However, before Julian could get away, he was captured by Markos again. In Home, Julian was used to demonstrate to Liz Forbes what happens to vampires (such as her daughter) who enter Mystic Falls, Virginia, which, thanks to the Travelers' spell, had been completely stripped of all Spirit Magic. He pushed Julian into the city limits, which resulted in Tyler's body first losing his vampirism, before then losing the magic that triggered his werewolf curse, leaving him as an untriggered werewolf for a brief moment before he ultimately died with a broken neck, the same way that he died when Klaus had turned him into a hybrid. However, Julian and Tyler's death ultimately resulted in Tyler's spirit being freed from the Passenger, and Tyler was able to go to the Other Side, where he was resurrected shortly afterward by Liv Parker and Bonnie.

Finn Mikaelson
In From a Cradle to a Grave, Esther placed Finn in the body of Vincent Griffith. In The Devil is Damned, he was killed by Elijah for trying to capture and kill Klaus' daughter Hope. Freya then resurrected him (and, by proxy, Vincent) in I Love You, Goodbye, and sealed his spirit in her talisman in They All Asked For You.

Kol Mikaelson
Esther placed Kol in the body of Kaleb Westphall in From a Cradle to a Grave, but this was not revealed until Rebirth. In Sanctuary, Finn hexed Kol, leaving him trapped in Kaleb's body with only a few days left to live. Though he and his loved ones tried their best to find a way to stop the hex, both Kol and Kaleb ultimately died in I Love You, Goodbye.

Rebekah Mikaelson
Esther wanted to place Rebekah in Cami's body in The Map of Moments. However, Kol redirected the spell and placed Rebekah into Eva Sinclair's body. Eva began to briefly take back control of her body in They All Asked For You and regained full control of her body in Exquisite Corpse. In the same episode, Rebekah destroyed Eva's consciousness and regained control of her body. In Fire with Fire, Rebekah killed Eva's body in an attempt to return to her original body, which ultimately succeeded. At the end of Ashes to Ashes, Freya revealed she had healed Eva's body and offered to place Rebekah's spirit back in this body once again, allowing her the chance to be both a human and a witch. She accepted Freya's offer and returned to Eva's body before vowing to find a way to bring back her brother Kol.

Dahlia
Dahlia was able to use Kenning to invade other peoples' minds like Jackson Kenner in Night Has A Thousand Eyes. She would later used the same spell on the reanimated body of Josephine LaRue in When the Levee Breaks.

Methodology

 * When a vampire possesses someone, they retain their powers of compulsion, as evidenced by Klaus' ability to compel students and Katherine while he was in Alaric's human body.
 * When a vampire is possessing someone, it allows them to bypass invitation barriers, as seen when Klaus, the Original Hybrid, and who was possessing Alaric, a human, was able to enter the Salvatore house without an invitation from Elena.
 * When a vampire is possessed, the person possessing them can enter through magical vampire-proof barriers, as seen with Esther, when she was able to enter through the Lockwood Cave, despite being in an Original vampire's body.
 * When a vampire possesses a witch, they are able to perform magic.
 * It is unknown if a human can perform body possession with help from a witch, since they do not have a supernatural hold.
 * When a witch possesses a vampire or hybrid, they gain their abilities, but lose their own ability to perform magic.
 * The Hollow appears to be an exception to this, although it is unclear how she achieved this.
 * Turning the host body into a vampire does not turn the spirit of the possessor.
 * Possession spells usually require a preparation spell beforehand on the host body.
 * The death of the host body is usually the only way to expel a spirit from possession.
 * Esther is the only witch so far to have shown that it is possible to leave the host body unharmed though it was a single instance.
 * Magic follows a witch into their host body as evidence by Céleste.
 * Travelers who passenger into humans retain their ability to perform magic.
 * It is unclear if the same applies to witches although Kol did not reject the idea when it was thought that Esther intended to jump into Camille's body.
 * Both Dahlia and The Hollow have proven this to be possible.
 * Possessed people are immune to mental intrusions such as Telepathy and Compulsion even from the likes of Silas due to having two minds in one body.
 * Although this may not be the case for Rebekah Mikaelson as Eva Sinclair's mind was destroyed and Rebekah was the only spirit in her body.
 * Spirits can possess inanimate objects like talismans as evidence by Finn.
 * The spirits of host bodies can sometimes reawaken and take back control though if powerful enough, some can not simply do so if not powerful enough.
 * Typically when someone possesses another, the possessor would exhibit traits and mannerisms similar to the host, seemingly by instinct. This makes it all the more difficult for them to be discerned.
 * Supernatural Hunters, having mental invulnerability, are naturally immune to possession as stated by Olivia Parker.
 * This suggests that possession has a mental aspect to it.
 * At least with oni, they have a harder time possession people with a "broken mind," such as Kurutta and Lizzie Saltzman, and the hosts could remember what happened while possessed and had some partial control of their faculties.

Types of Possession
There appears to be several different forms of possession:
 * 1) Spirit possession, the more common form which involves a witch casting a spell to allow a spirit to "jump" into another's body, which gives them full control of their new host body.
 * 2) Passenger spells, which are performed exclusively by the Travelers using Traveler Magic, and which, on its own, only gives the Passenger temporary control over their host body; in this case, the Passenger is called into control of their vessel by another person who says a set of "code words" to summon them. However, a spell does exist that gives Passengers permanent control of their host bodies, but it involves a Traveler casting a spell over the Passenger's own body, destroying it in the process and making it impossible to return to it. If this spell is cast, the only way to expel the Passenger from the vessel is to stab them with a Traveler Knife.
 * 3) Kenning, which has only been used so far by the ancient and powerful witch Dahlia. Kenning is a type of spell that allows a witch to temporarily possess the mind of one or multiple people, even from a distance, which allows the witch to see through their eyes to gain information and even control them to pass on messages.

Trivia

 * According to Josephine LaRue in They All Asked For You, witches despise possession when it is used against other witches.
 * It has been used so far in both The Vampire Diaries and The Originals by: Emily Bennett, Niklaus Mikaelson, Esther, Gregor, Katherine Pierce, Julian, Céleste Dubois, Finn Mikaelson, Kol Mikaelson and Rebekah Mikaelson, along with many other unnamed Travelers.
 * There are two known spells that specializes in spirit possession: Kenning and Passenger spells.
 * Emily is the first witch in the series to cast a possession spell.
 * Maddox is the first witch in the series to perform a possession spell on someone else's soul.
 * Season Six of The Vampire Diaries is the only season of which a witch does not perform a possession spell.
 * It is unknown why Florence could not be kept in by Jo's body as vampires have been shown to possess humans as well as mortal witches before (Klaus possessing Alaric, Esther intending Rebekah to possess Camille etc.). Although a few theories could be made:
 * Josette's vessel had not been cast with a preparation spell beforehand.
 * Josette was already dead while instances of such had always been with a live human.
 * Josette's body had been dead for a long time and was not perfectly preserved unlike Esther's with a spell
 * Such a possession can only be possible with an Original Vampire.
 * Florence was not born a witch unlike the Mikaelson Siblings.

The Vampire Diaries
Season One
 * History Repeating (Emily/Bonnie)

Season Two
 * Know Thy Enemy(Klaus/Alaric)
 * The Last Dance (Klaus/Alaric)
 * Klaus (Klaus/Alaric)
 * As I Lay Dying (Emily/Bonnie)

Season Three
 * Heart of Darkness (Esther/Rebekah)
 * Do Not Go Gentle (Esther/Rebekah)
 * The Departed (Klaus/Tyler)

Season Four
 * Growing Pains (Klaus/Tyler)

Season Five
 * Original Sin (Gregor/Matt)
 * For Whom the Bell Tolls (Gregor/Matt)
 * Dead Man on Campus (Gregor/Matt)
 * 500 Years of Solitude (Katherine/Elena)
 * The Devil Inside (Katherine/Elena)
 * Total Eclipse of the Heart (Katherine/Elena)
 * No Exit (Katherine/Elena)
 * Gone Girl (Katherine/Elena)
 * Resident Evil (Unknow/Liz, Julian/Tyler)
 * Man on Fire (Julian/Tyler)
 * What Lies Beneath (Julian/Tyler)
 * Promised Land (Julian/Tyler, Carl/Pam, Many other Travelers possessing humans)
 * Home (Julian/Tyler)

Season Seven
 * I Carry Your Heart With Me (Unknow/Oscar's body, Florence/Jo's body)
 * Live Through This (Unknow/Oscar's body, Florence/Jo's body)
 * Best Served Cold (Florence/Jo's body)
 * I Went to the Woods (Stefan/Marty's body, Ambrose/Stefan)
 * One Way or Another (Stefan/Marty's body, Ambrose/Stefan)
 * Somebody That I Used to Know (Beau/Lewis' body, Many other vampires possessing dead bodies)

The Originals
Season One
 * Always and Forever (Céleste/Sabine)
 * Tangled Up In Blue (Céleste/Sabine)
 * Fruit of the Poisoned Tree (Céleste/Sabine)
 * Bloodletting (Célest/Sabine)
 * The Casket Girls (Céleste/Sabine)
 * Après Moi, Le Déluge (Céleste/Sabine)
 * Dance Back from the Grave (Céleste/Sabine & Clara)
 * Crescent City (Céleste/Sabine)
 * Long Way Back From Hell (Céleste/Sabine & Clara)
 * Le Grand Guignol (Céleste/Sabine)
 * Farewell to Storyville (Céleste/Sabine)
 * Moon Over Bourbon Street (Céleste/Sabine)
 * From a Cradle to a Grave (Esther/Cassie, Finn/Vincent)

Season Two
 * Rebirth (Esther/Cassie, Finn/Vincent, Kol/Kaleb)
 * Alive and Kicking (Esther/Cassie, Finn/Vincent, Kol/Kaleb)
 * Every Mother's Son (Esther/Cassie & Lenore, Fin/Vincent)
 * Live and Let Die (Esther/Lenore, Finn/Vincent, Kol/Kaleb)
 * Red Door (Esther/Lenore, Finn/Vincent, Kol/Kaleb)
 * Wheel Inside the Wheel (Esther/Lenore, Finn/Vincent)
 * Chasing the Devil's Tail (Etsther/Lenore, Finn/Vincent, Kol/Kaleb)
 * The Brothers That Care Forgot (Finn/Vincent, Kol/Kaleb)
 * The Map of Moments (Esther/Lenore, Finn/Vincent, Kol/Kaleb, Rebekah/Eva)
 * Gonna Set Your Flag On Fire (Esther/Lenore, Finn/Vincent, Kol Kaleb, Rebekah/Eva)
 * Brotherhood of the Damned (Finn/Vincent, Kol/Kaleb)
 * Sanctuary (Kol/Kaleb, Rebekah/Eva)
 * The Devil is Damned (Kol/Kaleb, Rebekah/Eva)
 * I Love You, Goodbye (Finn/Vincent, Kol/Kaleb, Rebekah/Eva)
 * They All Asked For You (Finn/Vincent, Rebekah/Eva)
 * Save My Soul (Rebekah/Eva)
 * Exquisite Corpse (Esther/Lenore, Rebekah/Eva's Body)
 * Night Has A Thousand Eyes (Rebekah/Eva's body, Dahlia/Jackson and other)
 * When the Levee Breaks (Rebekah/Eva's body, Dahlia/Josephine's body)
 * City Beneath The Sea (Rebekah/Eva)
 * Fire with Fire (Rebekah/Eva's body)
 * Ashes to Ashes (Rebekah/Eva's body)

Season Three
 * Beautiful Mistake (Rebekah/Eva's body)

Season Four
 * High Water and a Devil's Daughter (The Hollow/Sofya)
 * A Spirit Here That Won't Be Broken (The Hollow/Hope)

Legacies
Season Two
 * Since When Do You Speak Japanese? (Oni/Kurutta, Samaritan, Dennis, Rafael, Landon, Lizzie)