Supernatural: The Most Game-Changing Episodes

TVLine rounds up the episodes the redefined Supernatural over its 15-season run with shocking twists, huge mythology reveals and major character introductions.

"In My Time of Dying" (Season 2, Episode 1)

When John made a deal with the Yellow-Eyed Demon and traded his life for Dean's, the sacrificial twist was not only tragic, but also raised the stakes of the show's mythology. Now having lost their father, Dean and Sam were truly on their own and had even more motivation to destroy the demon who had killed their mother.

"Lazarus Rising" (Season 4, Episode 1)

One of the most defining episodes of the series, the Season 4 opener introduced Misha Collins as the angel Castiel in grand fashion. With his memorable entrance came a brand new mythology that ushered in a bevy of heavenly players, including the existence of God himself — and the notion that He has a plan for the Winchesters.

"All Hell Breaks Loose: Part 1" (Season 2, Episode 21)

Sam died! That might not elicit the same kind of shocked reaction today as it did when the episode aired, given how many times the Winchester brothers have died over the seasons. But back in the show's early days, Sam's first death was a ballsy move that sent the message that anyone was fair game. It also propelled Dean down a path that would lead him to trade his life for Sammy's. (Hmmm, sounds familiar.) 

"In the Beginning" (Season 4, Episode 3)

There's something about Mary, indeed! When Castiel sent Dean back in time to the days of his parents' courtship, Dean discovered that his mother actually came from a family of hunters — and that she made a deal with the Yellow-Eyed Demon to save John's life, which ultimately led to her death years later. The revelation turned everything Dean — and viewers — knew about the Winchesters' maternal family history on its head.

"The Monster at the End of This Book" (Season 4, Episode 18)

The meta installment, in which Dean and Sam learn there are startlingly accurate novels written about their lives, was the first in a series of episodes that incorporated the fandom into the storytelling with tongue-in-cheek humor. (It's hard to imagine "The French Mistake" happening without this episode setting the stage for it.) The hour also planted several big mythology seeds with the introduction of Chuck the prophet and his so-called visions.

"Swan Song" (Season 5, Episode 22)

The Season 5 finale closed out the Winchesters' story with almost near finality, minus a "How is Sam alive?!" cliffhanger, which kickstarted a brand new chapter for the series after creator Eric Kripke departed as showrunner.

"As Time Goes By" (Season 8, Episode 12)

Unbeknownst to John, his father Henry belonged to the Men of Letters, a group that chronicled the supernatural, making Dean and Sam legacy members. And John and Mary were brought together by a higher power in a marriage of brains and brawns. Once again, Dean and Sam discovered that they really didn't know their family history as well as they thought they did  — but hey, at least this time, the brothers got a sweet home base out of it with the Men of Letters bunker!

"Don't Call Me Shurley" (Season 11, Episode 20)

While it was long suspected, viewers didn't get confirmation that Chuck was God until this Season 11 installment. Fans may have seen it coming, but Dean and Sam were shocked.

"Moriah" (Season 14, Episode 20)

How do you prep for a dramatic final season? Have God go bad by killing Jack and unleashing Hell on Earth, literally, as this episode did. After all, it doesn't get much bigger than the Almighty as your Big Bad.

"Do You Believe in Miracles" (Season 9, Episode 23)

Yes, Dean's time as a demon didn't last very long. But there's no denying that turning the hunter into the very thing he loathes and fights against was a daring change for a brief moment.

"All Along the Watchtower" (Season 12, Episode 23)

The birth of Lucifer's half-angel, half-human son Jack brought about the show's most significant cast addition since Castiel joined the ensemble. As a Nephilim, Jack represented a powerful new being in the supernatural playground and an unlikely new member of Dean, Sam and Cas' makeshift family.

"Alpha and Omega" (Season 11, Episode 23)

Many characters have come back from the dead over the seasons, but the return of Dean and Sam's beloved mother was one resurrection that no one saw coming. Having Mary back forced the brothers to reexamine their relationship with their mom, whom Sam never knew at all and whom Dean had put on a pedestal. Ultimately, Dean and Sam would lose Mary again, but in having her in their lives for as long as they did, they gained so much.

"All Hell Breaks Loose: Part 2" (Season 2, Episode 22)

Wait, he's really gone?! At the close of only the second season, Dean, Sam and a ghostly John defeated the Yellow-Eyed Demon, the main Big Bad who had plagued their family for decades. Rather than letting the plotline drag on for years, the writing team proved that they weren't afraid to shake things up by eliminating one of their main storytelling engines. (Little did viewers know that there would be 13 more seasons of new foes to battle, so they had no need to worry about how the show would carry on.)

"Despair" (Season 15, Episode 18)

The antepenultimate episode found all of Dean, Sam and Castiel's loved ones vanishing into thin air. Meanwhile, Cas realized what true happiness is for him and said an emotional, loving goodbye to Dean before giving himself up to The Empty to save the hunter from Death. Talk about dramatically altering the stakes ahead of the series finale!