Dean's crossroads deal and the rise of Lilith
7 episodes of Supernatural carry this thread, 7h in all — 4 of them are in The Essentials.
Arc membership is derived from each episode's own summary text, gated to the seasons the sources place each arc in. It shows where a thread is foregrounded, not every episode it touches.
In airing order
Bracing themselves for the possibility of an apocalyptic war, Sam and Dean realize they have an enormous task of hunting down the hundreds of demons that escaped from the Devil's Gate. With only a year left to live, Dean decides to live life to the fullest and exhibits a carefree attitude that troubles Sam, who is trying to find a loophole in the deal. Bobby tells the brothers about a sighting in Nebraska that turns out to be seven demons that are the actual manifestations of the Seven Deadly Sins.
Sam and Dean investigate a small town that has been plagued by a number of strange murders that resemble fairy tales, such as Little Red Riding Hood, Snow White and Hansel and Gretel. Meanwhile, Sam summons the Crossroad Demon and threatens to kill her with the newly rebuilt Colt unless she releases Dean from his deal.
It's Christmas time and Sam and Dean investigate a series of murders where the victims were pulled up through the chimney. Sam realizes they are dealing with a sort of Anti-Santa, a demon with roots in pagan lore. Dean wants to celebrate Christmas the old fashioned way as this is his last, but Sam refuses, not wanting to accept that Dean won't be around next year. Sam flashes back to a certain Christmas when he waited for his father to come home to give him a special gift.
Sam and Dean investigate the disappearance of a man who went missing at a tourist location. While searching the site, Dean is shot and killed by the owner. Sam is devastated but stunned when he wakes up the next morning to find Dean alive and well. As the day unfolds, Sam realizes he is re-living the previous day and tries to prevent Dean's death, but to no avail. Dean dies again and Sam must learn to live life without his brother by his side.
Dean is stunned after he receives a phone call from his dad who tells him he has a solution to get Dean out of his deal. Sam and Dean fight because Sam is skeptical that it is really John on the other end of the phone and warns Dean not to listen to him but Dean disagrees and sets off on his own path to follow his father's orders.
As time runs out for Dean, Sam convinces him to head to Eerie, Pennsylvania to investigate a possible zombie case. Instead, they discover Doc Benton, a real-life doctor who, in 1816, abandoned his medical practice to follow his obsession with finding the key to eternal life by drugging people and stealing their vital organs. Meanwhile, Bobby finds out where Bela is hiding, and Dean heads out to confront her, leaving Sam behind to deal with the good doctor. Dean and Bela battle it out for the last time, and Dean leaves Bela in a desperate, and possibly fatal, position.
It's 30 hours before Dean's deal with the crossroads demon is up and Dean, Sam and Bobby are searching for Lilith, who holds the contract. They discover her location and Sam summons Ruby for help despite Dean's protests. Ruby warns them they aren't ready to fight Lilith yet but they steal her knife and depart for New Harmony, Indiana. In a battle to the death, Sam, Dean and Bobby take on Lilith and all her demons in a last ditch effort to save Dean's life.