Sam's scar.
This scar on Sam's palm helps him decide what is real and what isn't. Using the pain, Sam can snap out of hallucinations, and come back to reality.
History
Sam first cut open his hand in Meet The New Boss when he remembers Hell, and falls on some broken glass. Dean bandages the wound. In Hello, Cruel World, Dean shows Sam how to use the pain from the scar to figure out what is real and what isn't. This is because pain in Hell is different from pain in real life. With this knowledge, Sam uses the pain from it to get rid of his hallucinations of Lucifer.
This seems to work for Sam so far. After the accident with the Leviathans, Sam zones out only once (The Girl Next Door), but is soon brought back by the pain from the scar. It is also briefly used and addressed in How to Win Friends and Influence Monsters when Sam is talking to Bobby how he's dealing with Hell. Sam begins to depend on the pain from the scar when Bobby's life is on the line in Death's Door.
When a case involving Demons comes up, Lucifer bothers Sam even more. Lucifer even helps Sam with the case, but with this, Sam let Lucifer in, making the power of the scar useless. Sam is no longer able to use the scar to get rid of Lucifer.
Used
- Season 7
- Hello, Cruel World
- The Girl Next Door
- Defending Your Life
- How to Win Friends and Influence Monsters (Not seen but used)
- Death's Door
- Repo Man (Used profusely)
Notes
- Sam tried to rub this scar again in "Hunteri Heroici", implying that he feared that his current situation was also a hallucination.
Trivia
- At a convention, Jared Padalecki and Jensen Ackles commented on how Sam and Dean get bashed up but always heal. But this time with Sam's hand it didn't. They comment on how they had a joke about CW cream that healed everything, but it looks like they ran out. Sera Gamble also commented that this scar will be permanent.