|“||The Shedim. (...) Hell's most savage. Things so dark and base, God himself would not allow them into the light. (...) Lucifer feared them, as well he should.||”|
The Shedim are an unknown type of supernatural being that were deemed too dangerous and subsequently trapped in an inaccessible section of Hell.
Long ago, Asmodeus sought to please Lucifer by freeing the Shedim as he believed that he could train and use them. However, since they were Hell's most savage creatures, even Lucifer feared the Shedim and subsequently locked them back up, and then scarred Asmodeus as punishment for disappointing him.
When Asmodeus claimed the throne of Hell after Crowley's death and Lucifer's entrapment in the alternate reality, he tracked down Jack and attempted to manipulate him into freeing the Shedim by shapeshifting into Donatello, the prophet. He said the Shedim were a troop of God's bravest soldiers and they were trapped in Hell and it was God's will to set them free. Jack managed to open the gate to Hell and the Shedim were almost freed but they were interrupted by Sam and Dean.
Shedim is the Hebrew word for demons or spirits and also designates a supernatural creature in Jewish folklore. The word shedim appears only twice (always plural) in the Tanakh, at Psalm 106:37 and Deuteronomy 32:17. It was possibly a loan-word from Akkadian in which the word shedu referred to a protective, benevolent spirit. Both times the term appears in the Tanakh, it deals with child or animal sacrifice to false gods that are called demons. The word may also derive from the "Sedim, Assyrian guard spirits" as referenced according to lore "Azael slept with Naamah and spawned Assyrian guard spirits known as sedim".
According to one legend, the shedim are descendants of serpents, or of demons in the form of serpents, alluding to in the serpent in Eden as related in Genesis. To others they are descendants of Adam and Lilith. Another legend said that God had started making them, intending for them to be humans, but did not complete their creation because he was resting during the Sabbath. Even after the Sabbath, he left them how they were to show that when the Sabbath comes, all work must be viewed as complete.
Shedim depiction in Supernatural, somewhat appear similar in the real lore depiction, in lore Shedim are said to have had the feet and claws of a rooster and share some characteristics both of human and angels. Like angels, they know the future and have wings, but like humans they eat, drink, procreate and die. They can also cause sickness and misfortune.
Supposedly, sinful people sacrificed their daughters to the shedim, but it is unclear if the sacrifice consisted in the murdering of the victims or in the sexual satisfaction of the demons. To see if the shedim were present in some place, ashes were thrown to the ground or floor, and then their footsteps became visible.
The shedim are supposed to follow the dead or fly around graves.
There are many things that one is admonished not to do in order to avoid invoking shedim, such as whistling or even saying the word "shedim." Rabbi Yehudah HaChasid wrote in his tzavaah that one should not seal up windows completely because it traps shedim in the house.
The relationship between Shedim and Asmodeus in Supernatural universe may be based from this lore: The shedim are not always seen as malicious creatures and are also considered to be helpful to humans. They are said to be even able to live according to the Torah, like Asmodeus.