Mark of Cain
Cain: The mark can be transferred to someone who's worthy.
Dean: You mean a killer like you?
Dean: Yeah, well, spare me the warning label. You had me at kill the bitch.
Cain: Yes.
Dean: Can I use it to kill that bitch?
Cain: Yes. But you have to know with the mark comes a great burden. Some would call it a great cost.
– Cain and Dean, 9.11 First Born
The Mark of Cain is a brand placed on Cain by Lucifer. 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 if the person is "worthy of it"; which is unspecified, but may mean being a killer, or something else. According to Cain, taking on the mark comes with a great cost and burden.
Contents
Episodes
9.11 First Born
Knowing that Dean wants the First Blade to kill Abaddon, and after seeing him kill a number of demons, Cain decides that Dean is "worthy" of carrying the Mark in order to wield the blade. Cain transfers the mark to Dean, where it appears on his right forearm. Cain warns Dean that carrying the mark will come at a cost.
9.12 Sharp Teeth
Dean and Sam have parted ways, but meet up at a hospital when they both find out Garth has been hospitalised. While there, Dean tells Sam about getting the Mark of Cain.
9.13 The Purge
Dean tells Sam that his research hasn't yielded any more information about the Mark of Cain.
9.16 Blade Runners
Finding the First Blade in the possession of Magnus, Dean is given the Blade by Magnus who wants to keep Dean as part of his "collection" as he is the only one who can use it due to the Mark. The Mark glows when Dean holds the Blade and it affects him strangely until he drops the Blade. Magnus tells Dean that he will get used to the feeling in time.
After Dean kills Magnus with the Blade, the Mark affects him strangely until he drops the Blade again.
9.17 Mother's Little Helper
Dean is feeling the after effects of invoking the power of the Mark of Cain when he used the First Blade. He's not sleeping, is obsessed with finding Abaddon - to the point of refusing to accompany Sam on a hunting trip - and his hands are shaking. Crowley suggests that using the Blade made him feel powerful and virile - but also scared.
9.18 Meta Fiction
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, "Dean, what did you do?" Dean demurs but Castiel grabs Dean's arm and pulls up Dean's sleeve to reveal the mark. "Damn it, Dean!" Castiel says, but without further explanation. After Dean gets into the Impala, Castiel tells Sam to watch over Dean.
9.19 Alex Annie Alexis Ann
Dean is shown to be able to overpower the vampire Connor with little effort, and slowly decapitates him with the blunt edge of his knife, presumably because of the Mark of Cain. Sam comments that Dean seemed to enjoy the kill a bit too much.
9.21 King of the Damned
Dean faces off against Abaddon armed with The First Blade. During the fight, he is able to kill another demon with the Blade but is pinned to the wall by Abaddon with telekinesis. The Mark, glowing brightly, provides Dean with immunity to Abaddon's powers with great concentration, but it doesn't last and he's pinned to the wall again without the Blade. With concentration, Dean is able to summon telekinesis with Mark's power and call the Blade into his hand. The Mark then grants Dean full immunity to Abaddon's powers and he is able to use the Mark and the Blade to finally kill her. The rage that comes with the Mark however causes him to stab Abaddon's corpse several times.
Mark of Cain in Lore
In the Abrahmic religions it is said that after killing Abel, God cursed Cain, saying that he would be forever separated from his family and become a nomad. The mark of Cain was said to be placed on Cain by God so "Therefore whoever kills Cain, vengeance will be taken on him sevenfold, and the Lord appointed a sign for Cain, so that no one finding him would slay him." (Genesis 4-14)
