Seven Deadly Sins
The Seven Deadly Sins are a group of black-eyed demons who seem to be the living personification of seven specific sins that humans commit. The origins of these demons are unknown, though they themselves claim to merely be natural human instinct. The demons are as follows: Envy, Lust, Greed, Pride, Gluttony, Sloth, and Wrath. Their relations to one another is not elaborated on. However, they appear to be on amicable terms with each other, and to be protective of each other. When speaking to hunters, Envy referred to his companions only as "the others" and knew that they were coming to rescue him.
The Seven Deadly Sins have shown several rare powers. Most notably, they have the unique demonic power to influence humans by filling them with their individual sin by touch, and then, with a suggestion, compelling their victims to dangerous and usually deadly acts based on that sin. The demons have also been implied to be telepathic, being able to read a person's memories without possessing her, and one demonstrated the ability to incite moderately strong seismic activity to shake the house they were in and break a devil's trap on the ceiling. However, they have all standard demonic weaknesses.
The Seven Deadly Sins are last on Earth during the Dark Ages, about five hundred years ago. In 1589, a man by the name of Peter Binsfeld becomes the first person to realize that the Seven Deadly Sins were not just vices but actual demons, and records this revelation accordingly. Around this time, the demons become trapped in Hell.
In May 2007, the Seven Deadly Sins are unleashed onto Earth once more when Jake Talley opens the Devil's Gate in Wyoming on Azazel's orders. Azazel means for them to serve as soldiers in a demon army led by Sam Winchester, known to the Seven Deadly Sins as "The Boy King"; however, after Azazel is suddenly killed by Dean Winchester, the Seven Deadly Sins disregard his plan and opt to enjoy their newfound freedom on Earth by inciting violent death among unsuspecting humans. A week later, they are found by hunters Sam, Dean, Bobby, Isaac, and Tamara, and a battle between both groups ensue; though the demons claim the life of Isaac, they are defeated, with Envy, Lust, Sloth, and Wrath getting exorcised back to Hell indefinitely by Tamara and Bobby, and Greed, Pride, and Gluttony getting killed by Ruby with her knife.
The Seven Deadly Sins in Lore
The early Roman Catholic Church divided sins into those which could be forgiven (venial sins) and capital sins which would result in eternal damnation unless confessed during the sacrament of Confession. Capital sins were known as deadly sins because they could have a fatal effect on an individual’s soul.
The seven deadly sins were formalized by Pope Gregory the Great in the 6th Century, although the concept of major human vices dated back to Greek times. They were, from most serious to least: pride, envy, anger, sadness, avarice, gluttony, and lust.
The statement in the show about Binsfeld discovering that the sins were actual demons in 1589, reflects the real-life Peter Binsfeld, in 1589, pairing each of the seven deadly sins with a demon who tempts people by means of the associated sin. According to Binsfeld's Classification of Demons, the pairings are as follows: Lust and Asmodeus, Gluttony and Beelzebub, Greed and Mammon, Sloth and Belphegor, Wrath and Satan, Envy and Leviathan, and Pride and Lucifer.
The Roman Catholic Church also recognizes seven holy virtues which correspond to each of the seven deadly sins. Vice: Virtue, Lust: Chastity, Gluttony: Temperance, Greed: Charity, Sloth: Diligence, Wrath: Forgiveness, Envy: Kindness and Pride: Humility.