|“||Your dad, he's in here with me. Trapped inside his own meat suit.||”|
Vessels, or Meatsuits, are physical living beings, usually humans who serve as the physical body or embodiment of spiritual, non-physical beings. At least some of these beings can be forcefully driven out through an exorcism while others can be driven out by the vessel.
Angels, of every variety, use possession as the means to interact with humans on Earth, and they require the vessel's permission before they can take any form of control, under a law mandated by God. Angels' true forms can fry humans to rotting corpses and their voices, outside vessels, can render humans deaf. Although, the angel's true vessels can withstand their respective angel's form and voices. Additionally, demons require vessels to interact on Earth in physical form, even to hold a conversation as noted by Mary Winchester.
Angels have multiple people that can be vessels for them, but only one person is their "true" vessel. While in a lesser vessel, an angel's abilities are limited when compared with their true vessel, and, as evidenced by Lucifer and Hael, may be damaging to the human. Archangels require their true vessel, otherwise they will burn out the body they are inhabiting. Not all humans are even compatible to house angels, and those who are incompatible and house them, will quickly degenerate and explode into blood, similar to the process of Molecular Combustion.
Possessing a person has a downside, as it renders them vulnerable to death by whatever they are vulnerable to by anyone that has that weapon. For example, an angel in a vessel can be killed by a human or a demon if they possess an angel blade when without a vessel, this would be impossible. When demons possess people, it also allows them to be killed when even an angel's powers are unable to kill them in their smoke form. However, the downside of this is that the person they are possessing is killed with them. If a demon's original human bones are burned, both they and their vessels are set on fire and burn to ash. In a unique case, Nick, the vessel of the archangel Lucifer, survived Lucifer being killed by an archangel blade. Sam Winchester speculated that this was because the blade was designed to kill the archangel within the vessel and not the vessel itself.
It is revealed that an angel that has become a human can themselves become possessed if they say "Yes." One angel believed that possessing Castiel in this way would make her stronger, but this is unconfirmed as Castiel killed her before she could force him to agree.
Demons possess the ability to restore their destroyed vessels with a ritual.
If a human bearing the Mark of Cain dies, he or she would be resurrected as a demon, with their former body serving as a vessel. This is demonstrated by Cain and Dean Winchester, both who became demons when they died bearing the mark.
More than one being may possess a vessel: for a short time, both Crowley and Gadreel possessed Sam Winchester before Sam expelled Gadreel and Crowley willingly left. Likewise, multiple Leviathans possessed Jimmy Novak for a short time, though the result was unstable. Later, Lucifer possessed Jimmy alongside Castiel and remained in control until Amara extracted him from Castiel. For a few minutes Lucifer, Crowley and Castiel possessed Jimmy at the same time, before the Winchesters exorcised Crowley.
According to Crowley, a person who is possessed can access the memories of the one possessing them and are aware of everything that being is aware of even if they don't remember it. With encouragement from Crowley, Sam is able to access a few of the memories of Gadreel. Caroline Johnson remarked on how she knew Castiel from Hannah possessing her. Dean recalled some memories of Alternate Michael possessing him.
Angel and demon vessels don't seem to age no matter how long they are possessed: Cain possessed his original body since his death and his appearance never changed, while a demon possessed Sister Agnes for over 50 years and she didn't age either. Castiel specifically told Jimmy Novak that he wouldn't age while possessed by him so it is the same with angels.
Both angels and demons can inhabit a dead person though given that angels need their vessel's permission, this is likely unique to Castiel as he was resurrected by God in the body of Jimmy Novak while Jimmy was not brought back. Lucifer, after being exorcised from Jefferson Rooney, was sent back into Nick's body by Crowley's perverted spell. While Nick's body had been repaired and improved to act as Lucifer's permanent vessel, Nick did not appear to have reconsented despite having been resurrected. This was presumably due to the nature of the spell modifications Crowley performed.
If an angel wishes, they are capable of granting their vessels powers when the vessel is in control and the angel is in the background. When Dean agreed to possession by the Apocalypse World Michael, Dean was granted several of Michael's powers while retaining control of himself. Included amongst these abilities was the power to kill an archangel with an archangel blade. Previously, only archangels were capable of killing each other with the blades.
It is revealed that a person can lock away the being possessing them, Sam took back control of himself while possessed by Lucifer long enough to send them both to the Cage. Castiel did a similar act to prevent Lucifer from killing Sam. In both cases, it was shown to be a struggling case. When Dean took back control, he imprisoned Michael in his subconscious in manner similar to Lucifer's Cage though he had to have complete focus on keeping Michael trapped.
It is law that angels use vessels to interact within the physical world. But in order for this to happen, the angel must first gain consent of their would-be vessel, who must voluntarily agree to the transaction, and no angel can disobey it, and thus will only take a willing vessel and will not and can not force themselves into a human like demons, thanks to the laws of God. Even archangels aren't exempt from this. Because of that, and the fact that most humans cannot stand the sight of an angel's true form, the angels have to find both willing and durable vessels.
After finding a potential host, the angel will then communicate with the human through visions in order to explain themselves and ask for the human's consent to gain control of their body. Such as when Castiel contacted Jimmy Novak through his household electronics and showed him a vision of what was to come. However, Lucifer tormented his vessel in order to get his consent through psychological hallucinations. Angels who have manifested within a vessel have superhuman abilities that easily surpass the power of a demon. It is unknown whether angels suppress their hosts like demons, but Jimmy described having Castiel inside him like being "strapped to a comet" and when Lucifer possessed Sam and let him speak, albeit through his own reflection, he referred to it as taking "the gag off." He later was able to speak to Jefferson Rooney inside his mind while possessing him. Dean told Sam that while Michael was possessing him it was like he was drowning and he lacked memory of the entire possession. After Castiel accessed some of his memories of the possession, Dean was able to remember more on his own later while talking with the alternate Kaia about Michael meeting her in his body. Additionally, while possessed, Dean managed to briefly manifest himself in a mirror to communicate with Michael, albeit after weeks of possession and for only a very short time before he was pushed down again. While possessing Adam Milligan, the Main Universe Michael was able to share control with his vessel in much the same way as Gadreel did with Sam. When Michael wished to speak with Adam, he manifested in the waking world as a duplicate of his vessel that was only visible to Adam himself. In this way, the two were able to hold conversations and arguments even when Michael wasn't in control. Additionally, its shown that active vessels, even while the human is in charge, don't require food or water though they are still able to enjoy it if they wish.
It has been shown however that if the vessel has enough strength of will, they can overpower the angel for at least a short time and retake control. This is true with demons as well, but for both the vessel must be exceptionally strong-willed. It's also been shown that an angel can choose to let their vessel take complete control and not even know that they are there but they can take control themselves when they wish without further permission.
Archangels however are much more powerful than regular angels and as a result their presence in a human "hollows them out" leaving a vacant empty shell once they leave the human, with recovery unknown. However, this may be more of a lack of care on the part of the archangel that causes this as Michael tells Dean that this won't happen to him if he allows Michael to use him as his vessel, despite Castiel saying that it will and that he will leave the young John Winchester who he is possessing "better than new." John is shown to be unaffected by the possession, though he was possessed for a shorter time than Raphael's vessel Donnie Finnerman who had also endured only a short possession and was left catatonic. If they aren't using their true vessel, the one they are using will decay over time, as shown with Nick. Other vessels used by Lucifer were burned out, appearing to be in a similar state to a being who has been smited. If an alternate vessel is only possessed for a short period of time, they may survive with little to no damage as shown with Jefferson Rooney after Lucifer was expelled from him. Dean Winchester, despite being possessed by the archangel Michael for weeks, suffered no ill effects to his health when Michael left his body aside from being weak at first though he quickly recovered. Though Nick survived Lucifer's destruction with his mind intact thanks to Crowley upgrading his body to act as a suitable vessel, Lucifer was determined to have done more damage to Nick's psyche than had previously been realized. This caused aggression and even occasional Lucifer-like mannerisms.
Angels can leave the host whenever they want to or if they are called away by the higher ups, leaving the vessel with little or no memory of the time they were occupied. The process also doesn't kill the human either as angels heal their vessel's wounds completely unlike demons whose vessels have their wounds return after the demon is exorcised or leaves. Also, as angels do not need to eat, a vessel may find themselves extremely hungry after being freed from possession.
A difference between angelic and demonic vessels is that while demons are unaffected by injuries to their vessels, they don't actually heal them and when the demon leaves their vessel through choice or exorcism, if the vessel has been fatally injured, the vessel will die. This tends to happen with vessels who have been possessed over a long period of time while vessels who have possessed for a much shorter period of time may survive, though traumatized. In the case of angels, when their vessels take injuries, they heal the injuries and the vessel will live if the angel leaves no matter how severe or fatal the injuries the vessel took over its possession. In one case an angel offered to use this aspect of taking a vessel to heal Sam Winchester of the damage he got from doing the Trials of God, something he could not heal by himself with his normal powers but apparently could with enough time through possession.
A vessel of an angel, due to their consent being needed for possession, can actually expel the angel possessing them if they wish to. Gadreel and Dean kept Sam from knowing of his possession by the angel to prevent this very thing from happening, but Sam, after learning of Gadreel's possession of him, managed to expel the angel once he knew the truth. Another aspect of this is that it's shown that even with a willing vessel if an angel leaves for any reason, they need the vessel's permission a second time when they return: Castiel needed Jimmy Novak's permission again after being pulled back to Heaven and Gadreel's original vessel had to give him permission once more when he was expelled by Sam. However, contrary to this, Lucifer did not need Nick's permission a second time after Crowley perverted a spell to send him back into Nick. This was possibly a consequence of the spell. Additionally, when Dean managed to manifest himself in a mirror while possessed by the archangel Michael, his attempt to order Michael out of his body had absolutely no effect on him and Michael only left on his own. Michael later revealed that Dean was actually fighting him so much that Michael chose to leave on his own before Dean could push him out in order to break Dean's spirit and prevent this. Michael was able to repossess Dean without a second "yes" because before he left Dean's body, Michael "left the door open a crack" which allowed him to return at will.
The British Men of Letters, using a combination of sorcery and technology, were able to create a device called a hyperbolic pulse generator capable of expelling both angels and demons from their vessels due to the inefficiency of exorcisms. This device is shown to be able to effectively exorcise even archangels.
- In the non-canon book Supernatural: The Men of Letters Bestiary: Winchester Family Edition, it is stated that all Special Children are suitable vessels for the archangel Lucifer.