Spoilers ahead for the Season 14 finale of Supernatural, called "Moriah."
Supernatural has a knack for ending seasons on crazy twists that leave fans speculating for months, and "Moriah" was no exception. The episode killed off a major character, revealed an unexpected character as a villain, and quite literally unleashed Hell on Earth. The fifteenth and final season has been set up, and it's safe to say that fans will have a lot to speculate about from now until Supernatural returns in the fall. Jack was killed by none other than Chuck, a.k.a. God.
Of course, Supernatural is no stranger to killing off major characters, and those characters are often known to be resurrected sooner or later. Still, sometimes the characters who bite the dust stay dead, and that already seemingly happened once in Season 14 when Jack accidentally killed Mary Winchester after burning off what was left of his soul. Killing Mary put him in the Winchesters' crosshairs.
After the penultimate episode revealed that not even the warded box designed to contain an archangel could hold the soulless nephilim once he decided to break out, and Dean came to the conclusion that the only way to stop Jack from using his considerable powers on innocent people would be to kill him. Castiel vehemently disagreed, and Sam was clearly conflicted, even if he did agree to Dean's plan.
The problem for the Winchesters was that they didn't know how to kill Jack even if they got their hands on him. All too conveniently, Chuck suddenly popped up with the solution, although not without acknowledging that his arrival is a literal "deus ex machina." He revealed that he created a weapon that could take Jack out: a gun.
It wasn't just any gun, and it was more complicated than the trusty Colt revolver. According to Chuck, whoever fired the gun would feel the same effects as the person on the receiving end. Whoever killed Jack would also die. Naturally, Dean decided it was his job to pull the trigger on Jack.
Meanwhile, Sam had a chat with Chuck, in which Chuck revealed that these versions of Sam and Dean are his favorites out of all of the many alternate universes he created, calling them "his favorite show" and saying "you're my guys." This made Sam suspicious, but he had bigger problems: Dean was gone, and so was the gun.
Dean found Jack (along with Castiel) in a graveyard, and Jack refused to flee. Flinging Castiel away with his powers, Jack knelt on the grass in front of Dean with the gun, and Dean cocked the gun. He couldn't bring himself to pull the trigger right away, and Jack forlornly naming himself "a monster" clearly didn't make Dean feel any better. The delay was long enough for Sam and Chuck to arrive on the scene, but Chuck refused to step in, saying that he was "enjoying" it.
Dean decided to lower the weapon of his own volition, which upset Chuck, who declared that the story isn't supposed to end with surrogate dad Dean refusing to put his "son" down. "This is Abraham and Isaac, this is epic!" yelled Chuck, and that was enough to clue Sam in that Chuck had been manipulating them all along for his own entertainment. All of their years of pain and suffering were because they were his favorite playthings to watch struggle.
Chuck made one last-ditch effort to get his way, telling Dean that he'd bring Mary back if Dean would just shoot Jack. Dean responded that Mary wouldn't want him to do such a thing, then told God to go to hell, and if that's not the most Dean Winchester way to end a season, I don't know what is.
So, Chuck snapped his fingers, causing Jack's grace to leave him, killing Jack. Sam picked up the gun and shot Chuck, but only hit him in the shoulder, so neither died. It did make Chuck mad, though, and he declared that the story is over and welcomed them "to the end." Oh, Supernatural. Always with the meta.
Night fell immediately, and an earthquake shook the cemetery. All the souls in Hell began to fly up into the sky. In a quick montage, the episode revealed a bunch of Sam and Dean's kind of enemies back on Earth, including a Woman in White and a killer clown. Monsters and demons galore popped into existence all over the place, and Team Free Will discovered that a cemetery was not the ideal place for this to happen.
All the bodies reanimated into zombies, and neither of the Winchesters had thought to bring John's old bat to take the zombies down, Negan-style. The zombies swarmed Sam, Dean, and Castiel, and it's safe to say that Jack won't be waking up to save them. He woke up in The Empty, with Billie turning up to say that they need to talk.