Gadreel

Gadreel is the angel that guarded the Garden of Eden from evil. He was imprisoned in one of Heaven's dungeons after his failure. After Metatron's spell, he posed as the famed angel Ezekiel, who was considered to be the exact opposite of Gadreel. While masquerading as Ezekiel, Gadreel inhabited Sam Winchester, as a way to heal the hunter and himself, but also to hide from Bartholomew and Malachi.

Background
Gadreel was once God's most trusted angel. He was stationed at the Garden of Eden to protect it from Lucifer's corruption. However, he failed at this task and so was dishonored. His failure was considered so severe that he was locked in a dungeon in Heaven for thousands of years.

I Think I'm Gonna Like It Here
Gadreel fell to Earth with the other angels and took a vessel, but is injured and weakened by falling. When Dean lets out a desperate prayer to any angel to help Sam, Gadreel, who is traveling by bus, hears the prayer and gets back on the bus to help.

After Gadreel arrives at Dean's location, he interrupts an angel that is attempting to get Castiel's location out of Dean. However, when the angel attacks Gadreel, he is no match for him. Dean kills the angel with his own Angel Blade and Gadreel passes out.

While he is unconscious, Dean traps him in Holy Fire and demands to know what he wants as he is distrusting of angels, given what happened with the other angel. Gadreel, identifying himself as "Ezekiel", convinces Dean he wants to help and Castiel later confirms by phone that "Ezekiel" can be trusted, so Dean lets him try. However, both Gadreel and Sam are weak and he is unable to heal him right away.

Two angels arrive and Dean puts up warding to protect Sam and Gadreel as Sam can't leave without dying and manages to banish the two angels who show up. With Sam near death and unable to do anything, Gadreel offers a "bad" solution: he possesses Sam. Doing so would allow him to heal Sam from the inside while recuperating from his own injuries. After showing Dean how close Sam is to giving up, Gadreel takes on Dean's form and enters Sam's mind, convincing him to say "Yes" to him. Gadreel possesses Sam and leaves the hospital with Dean, leaving his previous vessel there with no memory of what happened.

Gadreel decides to let Sam remain in control of his body while he hides away in his mind, but warns Dean that Sam must not know until he can accept it or he will be able to eject the angel from him, especially in Gadreel's weakened state. Gadreel and Dean decide to erase Sam's memory of his near-death experience and Gadreel gives Sam back control.

Devil May Care
When Sam is knocked out by three demons, Gadreel takes control of his body and displays what's left of his wings, and distracts them with the light it causes. Gadreel then uses the Demon-killing knife to kill them in order to avoid questions when Sam wakes up. Gadreel's presence causes Abaddon to flee and he and Dean discuss the situation with Dean admitting that he feels guilty about all the deaths that have happened as he stopped Sam from sealing up Hell. Gadreel tells Dean that he understands that he did it to save Sam and that he loves his brother a lot from being in Sam's mind and keeps Sam from knowing what happened while he was knocked out after he gives up control again, having used the knife to kill the demons so Dean could explain away their deaths.

I'm No Angel
Gadreel takes control of Sam to warn Dean that the angels are looking for Castiel and that a faction is gaining vessels and power. He also reassures Dean that Sam is feeling better and that he is successfully healing him though it is slow going. Dean grows worried about the angels chasing Castiel, but has Gadreel give back control to Sam rather than continue helping.

When Dean gets desperate to find Castiel after learning that Reapers are after him, Dean calls on Gadreel to help. Gadreel reluctantly takes control, telling Dean that he can't be running around in control, but Dean asks him to just help to find Castiel. Gadreel is unable to do so due to Castiel warding himself with a tattoo against angels, but Dean instead has him look for Reapers that are after Castiel. Gadreel is able to locate Castiel this way and gives back control to Sam.

After Castiel is killed by the Reaper and Dean kills the Reaper, Gadreel once again takes control of Sam and resurrects Castiel. Dean covers it up by claiming that Sam got knocked out and then he made a deal with the Reaper not to kill her if she brought Castiel back and then killed her anyway.

At the Men of Letters base, Gadreel takes control and tells Dean that Castiel must leave because angels are after him and while the base is protected, they can't withstand an incursion. Gadreel tells Dean that if Castiel isn't sent away he will have to leave Sam and flee which would lead to Sam's death. With no other choice, Dean tells Castiel he has to leave.

Slumber Party
When Charlie Bradbury is killed by the Wicked Witch, Dean calls out to Gadreel as soon as Sam enters the room and he takes control. Dean asks for help with Charlie, but Gadreel tells him that Charlie is dead and he can't keep using his powers to help as it weakens him and he is only back at half-strength. He tells Dean he can either bring Charlie back or help with the Witch and Dean has him resurrect Charlie. Dean then tells Sam and Charlie that they got knocked out by the Witch but he drove her off. However Sam becomes suspicious as he heard Dean call for a "Zeke" but Dean tried to say that Sam was out of it.

Dog Dean Afternoon
After Chef Leo slashes Sam's neck, seriously wounding him, Gadreel takes control for a moment to heal the wound and erase Sam's memory of it. As a result, Chef Leo tries to eat Sam to heal his own cancer.

Rock and a Hard Place
When Dean prepares to tell Sam about Gadreel, the angel quickly takes possession of Sam and tells Dean that Sam is not ready to know the truth, but also promises that he will not be in Sam much longer.

Holy Terror
He again promises Dean he won't be in Sam much longer. He is not happy when Castiel comes back and asks Dean to get rid of him. While at a bar, he goes outside to get some air where he is met by Metatron who tells him he know who he really is. Metatron tells him that he wants to bring back Heaven to it's former glory and wants him to be his second in command so that he can redeem himself for his failure saying that he used to be God's most trusted. After many secret meeting with Metatron he accepts the offer, Metatron is glad and gives him a piece of paper with a name on it telling him to kill said person. Gadreel says that's not who he is but Metatron says it must be done.

Meanwhile, Dean has figured out the truth from Castiel and asks Kevin to help him find a way to cancel the angel out so that he can tell Sam the truth. They find special sigils and paint them in the storeroom. Dean brings "Sam" to the room and activates the spell and tells him the truth, he gets really upsets and starts to leave Dean tries to stop him but Sam punches him out.

"Sam" approaches Kevin and proceeds to smite the prophet. Dean witnesses this in horror and tries to aid, but "Sam" telekinetically pins him to a pillar. Gadreel reveals that he was in possession of Sam's body the whole time they talked and that he tampered with the spell so that it was Sam's spirit that was expelled, not his. After revealing the truth to Dean, Gadreel pulls out the paper Metatron gave him and placed it on Kevin's body, revealing the name written on the paper to be Kevin's. Gadreel then proceeds to leave the bunker with the angel and demon tablets.

Personality
Gadreel was once God's most trusted and reliable angel. He was well-meaning and benign. However, after his failure to prevent evil from infecting the Earth, Gadreel was dishonored.

In his initial appearance, Gadreel imitated what he interpreted as Ezekiel's personality; the stereotypical interpretation of an angel, as he was humble and polite as opposed to being arrogant and condescending like many other angels. He claimed to see angels as beings of compassion, not wrath. He speaks with a calm, soothing voice and was extremely pacifistic, but would engage in violence if necessary. When Dean informs Castiel of "Ezekiel's" appearance, Castiel calls him a good soldier and believes he can be trusted, Castiel also implies they're friends. Gadreel also proves to be quite intelligent, using the demon killing knife instead of smiting the three demons, so Sam wouldn't be suspicious of their deaths. He also seems somewhat annoyed at being called Zeke. Despite his apparent compassion, he has a self-preservation instinct, which shows when he gives Dean an ultimatum: send Castiel away, or he will leave Sam, killing him, to save himself from Bartholomew. Despite this and his weakened state, he is compassionate to a fault, shown when he resurrects Castiel and Charlie despite knowing it will weaken him because Dean was distraught by their deaths.

After his true identity is revealed, his personality shifts significantly. It is revealed that he took possession of Sam both for healing purposes, and to hide from Bartholomew and Malachi, but also to make amends for his past mistakes and failures. Despite the stigma he received in Heaven, Gadreel does have some inherent benevolence. When Metatron tasked him to smite Kevin Tran, Gadreel stated that killing the innocent was not who he was. Despite this, Gadreel did as he was told, smiting Kevin, and showing great remorse in doing so.

Powers & Abilities
Gadreel possesses the common powers of an angel. According to him, he was severely injured when he fell, which left him considerably drained and weakened, as seen when he was easily bested by another fallen angel. However, after regaining a portion of his original strength, he was capable of fighting off and defeating three demons in physically powerful human hosts. Despite having been expeled, Gadreel retained his powers as an angel, similar to Castiel in his second fall, implying that Gadreel may be a higher class angel.
 * Immortality - Gadreel is thousands of years old. He was present at the Garden of Eden.
 * Super Strength - After his fall, Gadreel retained just enough of his original strength to sufficiently overpower three low-level black-eyed demons at once; as shown when he single-handedly shoved one away with above-average force. However, in his weakened state at that time, he was no match for another fallen angel. His strength is gradually returning, though he was barely back to half-strength during the events of Slumber Party, though he implied that he was strong enough to help defeat the Wicked Witch. As of Holy Terror, his strength is almost completely restored.
 * Regeneration - Gadreel heals his vessel's wounds, even mortal ones, in moments. Using this power, he can heal a vessel of damage even to the subatomic level while at the same time healing himself. However, in his weakened state this takes time though he is slowly making progress. A serious neck wound required him to take complete control to heal, but he was able to do it in seconds.
 * Healing - Gadreel can cure the bodily wounds and illnesses suffered by others, even those of a supernatural origin. However, in his weakened state if the person he is healing is weak as he is, he is not able to do this. When he resurrected Castiel, he healed his wound and the ones he got from torture.
 * Electronic Manipulation - Gadreel caused the alarms on a machine connected to Sam to turn off with just a wave of his hand.
 * Smiting - He killed Kevin in the same way he would a demon, by touching his forehead.
 * White Light - Gadreel used this power in Devil May Care against a group of demons. The blast was such that it surprised Abbadon, a Knight of Hell.
 * Telekinesis - Gadreel was able to pin Dean to a wall with just a wave of his hand and keep him there without any apparent concentration. He released Dean by simply walking away.
 * Memory Manipulation - Gadreel erased Sam's memory that they met in his mind and also that he gave Gadreel permission to possess his body.
 * Angelic Possession - As an angel, Gadreel needs a willing living human vessel to physically exist on Earth. As of right now, Gadreel is possessing Sam Winchester's body to keep him alive.
 * Telepathy - Gadreel can tap into "angel radio" as well as read the minds of humans, but only with physical contact. By placing a hand on two persons, he can let the first person listen to the thoughts of the second.
 * Astral Projection - Gadreel is able to display the remains of his wings, causing a massive flash of white light.
 * Super Senses - Gadreel is able to find a warded Castiel by locating a Reaper who is holding him captive. Like the other angels, he can hear humans prayers and can sense their location.
 * Resurrection - Gadreel is able to bring those who have died back to life, or at least those who have been dead for a short period of time. So far, he has demonstrated this ability on Castiel and Charlie Bradbury.

Weaknesses
Gadreel possesses the standard weaknesses of an angel.
 * Angel Banishing Sigil - An Angel Banishing Sigil could banish him.
 * Enochian Sigils - Certain Enochian Sigils can weaken him and keep him from finding people.
 * Angel Exiling Spell - Metatron's spell cast Gadreel to Earth.
 * Enochian Spell - An Enochian spell could effectively knock him out for a period of time and keep him from knowing what's going on.
 * Holy Fire - Dean imprisoned Gadreel in a circle of holy fire during their first meeting.

Appearances

 * Season 9
 * I Think I'm Gonna Like It Here
 * Devil May Care
 * I'm No Angel
 * Slumber Party
 * Dog Dean Afternoon
 * Rock and a Hard Place
 * Holy Terror

Trivia

 * Gadreel is listed as one of the chiefs in the fallen Grigori of angels, also known as the Watchers. This is depicted in the second section of the Book of Enoch; "Parables". He is said to be responsible for teaching man warfare. This is contradictory to the first section of Enoch, which claims Azazel to be responsible for this.
 * Gadreel's angelic shadow form can be seen behind Sam on the barn in the Season 9 poster as well.
 * When Gadreel resurrects Castiel and heals his wounds, his hand glows in a similar manner to that of Leo Wyatt in the TV series Charmed whenever he healed someone. Leo was a Whitelighter, a type of human angel, but did not possess the power to resurrect the dead like Gadreel. Castiel's hand also glowed in a similar manner when healing an orderly in "Hunteri Heroici," but these are the only two times this has been seen on Supernatural.