Changes

According to [[Death]], before there was life, the Earth, or even God and the [[archangels]], there was [[the Darkness]]. God and His archangels defeated the Darkness and locked it away rather than destroy her to maintain [[the Cosmic Balance]]. God created the Mark to act as the lock and key on to the Darkness' cage and if it is was to destroyed, the Darkness will would be released. God gave the Mark to his most trusted lieutenant, [[Lucifer]], but the Mark corrupted Lucifer and made him jealous of humanity which led to his imprisonment in [[Lucifer's Cage|the Cage]]. Prior to being locked away, Lucifer eventually passed the Mark to [[Cain]] as part of his deal to save Abel from Lucifer's influence.

After Cain was given the Mark, he begins began to realize what kind of toll bearing the Mark will would take after he killed Abel, and rather than be controlled by his murderous compulsion, he attempts attempted to kill himself with the First Blade. However the Mark would not let his [[soul ]] depart to the afterlife. After Cain's soul was twisted and corrupted by the Mark's dark, influential, primal energies, he was reborn as a [[Knight of Hell]], the very first of his kind. He goes Cain would go on to train and lead use the Mark to corrupt a group of damned souls handpicked by Lucifer to be the Knights of Hell under Lucifer's command. Cain became their commander, as they wreacked training the Knights to wreak havoc on Earth for centuries as the harbingers of chaos and darkness.<ref name="nine11">[[9.11 First Born]]</ref> .

After centuries of murder and mayhem, he Cain fell in love with [[Colette Mullen]]. The Knights took retribution and took Colette, so forcing Cain used to use the First Blade and its energy drawn from the Mark to slaughter all the Knights except for one; [[Abaddon]]. Despite Colette's death by Abaddon's hands, Cain manages managed to cease killing, keeping his final promise to herhis wife. After burying his wife, after he Cain disposed of the First Blade in the Mariana Trench.

The Mark is the source of [[the First Blade]]'s power, and imbues its owner with great strength and an almost insatiable desire to kill. This strength is enough to overpower an entire nest of [[vampires]] and even [[Castiel|an angel]]. It is the source of [[the First Blade]]'s power. The Mark and the Blade work together, and without it the First Blade is rendered useless. The Mark can also be transferred to someone else if the person is worthy of it; a killer like Cain. While the Mark is a corrupting influence, [[God]] revealed to Lucifer that the Mark does not change the bearer, but merely amplifies and intensifies what is already there. Which in Lucifer's case was his dislike antipathy of humanity.

The Mark's existence keeps kept [[the Darkness]] bound. If When it is was removedwithout being transferred to someone else, the Darkness will be was released from its confinement.

After gaining the Mark, [[Dean]] began to exhibit more aggressive behavior, and once the Mark was activated by the First Blade his aggression was amplified. Once he began killing with the First Blade, the burden of the Mark became apparent -- the more Dean kills the better he will feel, the less he kills the worse he will feel, and if he does not keep killing it will eventually cause his death. Because , as Crowley informs Dean, the human body was never meant to contain the First Blade's power.

After [[Metatron]] kills him, Dean is resurrected by the power of the Mark and the First Blade. It has , which twisted his soul until it is was demonic. As a demon Dean shows showed no care for anyone or thing -- not even Samor the Impala. The Mark of Cain also bestows bestowed an invincibility onto Dean's body, which has been shown to be able to heal from any wounds inflicted upon it. Crowley reveals to Dean that the Mark needs to be sated with killing, or Dean will become even darker.

Sam is was able to [[Demon Cure|cure]] Dean and revert him of being back to a Knighthuman, however, he Dean still possesses possessed the Mark. After seemingly being unaffected by the Mark for months, its powers started to affect Dean again, giving him a precognitive nightmare of a massacre of humans he committed under its influence a few days later. Unable to find any way in the lore to stop the Mark's influence, Castiel retrieved Metatron from his incarceration in Heaven. Metatron refused to provide any information, however as Dean tortured him, Metatron tells him, "The river shall end at the source." Sam suggests to Dean that he needs to find a power within himself to resist the influence of the Mark.

Unable to find any way in the lore to stop After killing Abaddon's demons, Cain fell back under the Mark's influence, Castiel retrieves Metatron from deciding to slaughter his own descendants as he felt his incarceration in Heavenbloodline was "tainted" by the stain he released upon the Earth -- murder. Metatron refuses to provide any informationTo stop him, however as Dean tortures , Sam, [[Castiel]] and Crowley teamed up, imprisoning himin a [[devil's trap]] which limited his powers but didn't block them completely. After Cain was trapped, Metatron says "the river shall end at two bearers of the source". Sam suggests Mark faced off in a fight to the death which Dean won, killing Cain who claimed that he needs to find a power within himself to resist the influence of there was no cure for the Mark.

After Following his killing Abaddonof Cain, the Mark's demonsinfluence on Dean grew even stronger, nearly being completely consumed by its power. The toll of the Mark would lead to Dean having nightmares all the time, Cain fell back including nightmares of those he killed under the Mark's influence, deciding . This led Sam and Castiel to slaughter his own descendants as interrogate Metatron who admitted he felt his bloodline was "tainted" by doesn't know of a cure for the stain Mark, and only said what he released upon said to stop further torture. After a run-in with the Earth, murder. To stop him, Dean, Sam, [[CastielStyne (family)|Styne family]] and Crowley teamed up, imprisoning him Sam became engaged in a obsessive but mostly futile attempt to crack the ''[[devilBook of the Damned]]'' behind Dean's trapback. Following [[Charlie Bradbury]] which limited his powers but didn't block them s murder, Dean appeared to have given into the Mark completely. After Cain was trapped, brutally murdering the two bearers of the Mark of Cain faced off entire Styne family in a fight revenge, even [[Cyrus Styne|an innocent kid]], and nearly murdering Castiel when he tries to the death which help Dean remember his humanity. Dean wonwas able to find enough control to stop himself from killing his friend, killing Cain who claimed that there was no cure for the Markhowever he warned Castiel and Sam to stay away from him or he will kill them next time.

Following his killing of Cain, the Mark's influence on Dean has grown even stronger, and he is close to being completely consumed by its power. He is also having nightmares all the time, including nightmares of those he killed under the Mark's influence. This leads Sam and Castiel to interrogate Metatron who admits he doesn't know of a cure for the Mark. After a run-in with the [[Styne (family)|Styne Family]], Sam has engaged in obsessive but mostly futile attempts to crack the ''[[Book of the Damned]]'' behind Dean's back. Following [[Charlie Bradbury]]'s murder, Dean appears to have given into the Mark completely, brutally murdering the entire Styne Family in revenge, even [[Cyrus Styne|an innocent kid]], and almost annihilating Castiel when he tries to help Dean remember his humanity. Dean finds enough control to stop himself from killing his friend, however he warns Cas and Sam to stay away from him or he will kill them next time. After the Mark makes Dean allow his fellow hunter , [[Rudy]] , to die, Dean summons [[Death]] to kill him or remove the Mark. Death explains the Mark's purpose to Dean and makes an offer: he will transport Dean someplace where he will no longer be a threat -- but only if Dean kills Sam first. Dean kills Death instead, and the Mark is removed by [[Rowena]], releasing [[the Darkness]].

Dean rubs his arm once early in the episode, as though the mark is sore or bothering him. Towards the end of the episode, Castiel asks if Dean is okay, sensing something; then asks him, "Deandemurs, what did you do?" Dean demurs but Castiel grabs Dean's arm and pulls up Dean's sleeve to reveal the markthen asks him "What have you done?" and Dean justifies it as the means to an end. "Damn it, Dean!" Castiel says, but without further explanation, Dean leaves telling him that while Castiel locates Heaven, he has a Knight to kill. After Dean gets into the Impala, Castiel tells Sam to watch over keep an eye on Dean.