Soul

A soul is a person's essence, and what persists after death. In Supernatural, a soul separate from its body is visualized as a blinding white light.^{5.14 My Bloody Valentine}

According to Death, human souls are very powerful and very meaningful essences even when it exists outside the body. They can be corrupted and managed, and according to Death, they can sustain itself after being tortured, and they cannot be destroyed by even Death himself^{6.11 Appointment in Samarra}

According to Death, a Soul is extremely powerful, even without its human body, and they are corruptible, and it's impossible to undo certain damage which a Soul has endured. But he tells Dean that he can't undo the damage done to Sam's soul, but he says that he can insert a mental barrier in Sam's mind that would hide the torment that his soul endured while existing in the Cage with Michael and Lucifer; the mental barrier, however, will eventually subside.

File:Human Soul.jpg

The actual essence of a human - Soul

After Death

Most spirits are transported by reapers after death to the next destination. Those who refuse to move on can become ghosts or vengeful spirits

Hell

Demons are formed in Hell by the corruption of a human soul over time. Lucifer made Lilith into the first demon in order to mock God's creation of humanity. While in Hell, Dean eventually broke under Alastair's torture and started torturing souls himself, and so likely would have been transformed without Castiel's intervention.

Heaven

In Heaven, each soul has its own version of Heaven where he or she relives happy memories. Heavens are individual, except in the case of soulmates, who share the same Heaven, according to Ash. Most souls cannot leave their own allotted space.^{5.16 Dark Side Of The Moon}.

Purgatory

Purgatory is a spiritual realm where the souls of supernatural creatures go after they die. This place is not connected with Heaven or Hell, though it has been referred to as "hell adjacent".

After resurrecting Samuel Campbell, Crowley has him tracking down high-ranking creatures, especially Alphas, so that he can question them about the location of Purgatory, which he wants for "development purposes."

Deals and Markers

Souls are first mentioned explicitly in Supernatural in relation to the deals made by Crossroads Demons, wherein a person agrees to give their soul to the demon upon death in exchange for some benefit when they are alive. Crowley was originally the head Crossroads Demon. The deals are traditionally sealed with a kiss, and have a set time limit at the end of which the subject of a deal, if still living, is killed.

John Winchester sold his soul to Azazel in exchange for Dean's life ^{2.01 In My Time Of Dying}, and Dean did the same for Sam.^{3.16 No Rest For The Wicked} Sam attempted to sell his own soul to bring back Dean, but was refused.^{4.09 I Know What You Did Last Summer} Bobby sells his soul to Crowley to get information on Death's whereabouts in order to help stop the Apocalypse. The deal is undone when Bobby, with help from Sam and Dean, threatened to destroy Crowley by burning his bones.^{6.04 Weekend At Bobby's}

See the Crossroads Demon entry for a list of deals made.

Balthazar bought the soul of a boy, Aaron Birch, in exchange for a part of the Staff of Moses. It is unclear why he wants the soul, though he refers to souls as the only thing left of value, and he is eventually forced to return it.^{6.03 The Third Man}

In claiming Aaron's soul, Balthazar left an identifying mark on it. Castiel has the ability to 'read' a person's soul, and sees the mark of the other angel when he reads Aaron. Castiel can also identify the absence of a soul, and is therefore able to determine Sam's soulless state in 6.07 Family Matters. Crowley is also able to make the details of the contract he made with Bobby manifest as writing on his skin.^{6.04 Weekend At Bobby's}

Famine

In 5.14 My Bloody Valentine, the Horseman Famine sends a demon to retrieve a soul for him to consume which would strengthen him, and the demon transports the soul in a briefcase. Sam later confronts this demon, which it flees, leaving behind the briefcase which contained a human soul. This demon later reports back to Famine and informs the Horseman that he lost the soul to which Famine ruthlessly exorcises the demon and consumes its soul instead.

In 5.14 My Bloody Valentine, the Horseman Famine pears inside Dean and reveals that the reason Famine's power which affects humans' urges didn't affect Dean is because he is already dead inside.

Sam's Soul

Castiel: Somehow, when Sam was resurrected, it was without his soul. Dean: So where is it? Castiel: My guess is still in the cage with Michael and Lucifer. Dean: So is he even still Sam? Castiel: Well, you pose an interesting philosophical question. – Dean and Castiel discuss Sam, 6.07 Family Matters

Since his return from Lucifer's Cage, Sam appears different, especially to Dean. He seems to exhibit little compassion or emotion and Dean becomes increasingly suspicious that Sam may be either possessed by Lucifer (which Castiel is able to refute ^{6.03 The Third Man}, or another creature. It is eventually Veritas who confirms that Sam is "not human" and gets Sam to admit that he knows something is deeply wrong. ^{6.06 You Can't Handle The Truth}

Dean calls on Castiel who ascertains that the reason Sam is feeling no emotion, and no longer sleeps, is that he was resurrected without his soul.^{6.07 Family Matters}

Crowley claims that he pulled Sam out of Lucifer's Cage, but kept the soul "hostage" and that he will return Sam's soul if the Winchesters help him find Purgatory - a task he has had Samuel Campbell working on since his resurrection. Crowley later reveals to Dean, Sam and Castiel that he is incapable of raising Sam's soul from Lucifer's Cage, stating that raising Sam's body from the Cage was a very difficult task to preform.^{6.10 Caged Heat} Castiel and Crowley both intelligently predict that Sam's soul is more than likely be tormented and tortured by Lucifer and Michael, in which consumption of it could severely alter Sam, more specifically, it would drive him insane, and as Castiel put it, Sam would feel trapped inside his own body to which would more than likely result in occurrences of catastrophic events that would devastate Sam and others around him.

For a while Sam continues to insist to Dean that he is still Sam - "same melon, same memories" - just without his soul but Dean finally confronts Sam:

Dean: I mean, it's your gigantor body and and maybe your brain, but it's not you. So just...stop pretending. Do us both a favor.

Sam finally admits that "I'm not your brother. I'm not Sam". Then he confesses that while he doesn't think having no soul is "better or worse, just different", but decides that he sould get his soul back.

Sam: I was that other Sam for a long time, and it was kinda harder. But there are also things about it I remember that... Let's just say, I should probably go back to being him. Dean: That's very interesting. It's a step. Sam: So? Dean: We do what we gotta do. And we get my brother back. – Dean and Sam, 6.08 All Dogs Go To Heaven

In 6.09 Clap Your Hands If You Believe, the Leprechaun senses Sam's lack of soul.

Leprechaun: The human soul gives off a certain perfume. Your soul is far away, but not completely out of reach.

He says that he could get Sam's soul out of Lucifer's Cage, but Sam banishes him.

Sam is eventually reunited with his soul in 6.11 Appointment in Samarra when Death himself liberates it from Hell and personally delivers it back to Sam's body, despite his protests. Death installs it with the promise that a wall will be erected in Sam's mind which will prevent him from remembering his torment in Hell, but advises him to not "scratch away at it", lest the wall collapses and his memories come flooding back (though he suggests that this may happen over time regardless). Prior to this, Sam seeks a way to permanently keep his soul separated from his body. Balthazar instructs him in the use of a spell that will scar his vessel, but can only be completed by committing patricide, stating that "A father's blood is needed but the father need not be blood"; meaning that a father figure is sufficient, or Balthazar could have been lying to cause chaos between Sam and Dean.

It is also possible that given the length of time he spent in Hell (120+ years) and the extremity of his suffering, Sam's soul has been corrupted and is now demonic. Though there is no evidence to confirm this, it is noteworthy that both Castiel and Balthazar were less than optimistic about its condition; and that even Crowley, himself a demon and therefore well-acquainted with pain and corruption, would rather "swallow a filthy shower rag" than have Sam's soul returned to him.

Souls in Religion and Lore

• The key events in the 1.01 Pilot - the night when Sam is fed Demon Blood by Azazel, and Mary dies, and also the night Jessica dies - occur on November the second which is known as All Souls Day.
• The soul in religion and philosophy from the Catholic Encylopedia
• Wikipedia entry on souls.