Summary

• The pilot episode sets the tone with a tragic murder that fuels Sam's motivation.
• Sam's death at the hands of Azazel marks the beginning of a trend of resurrection.
• The Men of Letters' introduction provides a new base for Sam and Dean in Season 8.

Over 15 years, Supernatural developed into an epic story of brotherhood, and friendship, with plenty of mystery and death along the way, but the show did have some moments that defined it along the way. Supernatural began airing in 2005, and from the beginning, the show proved that it would be packed with excitement, drama, and fun. Sam and Dean Winchester are introduced as two young, but highly skilled hunters who make it their business to confront the demons and monsters that roam free in the world.

While the show initially delivered a monster of the week, serialized story that felt like a procedural in some ways, it also had a larger plan for where the Winchester boys would end up. Building on some core mysteries, seeing Sam and Dean grow closer together as brothers, and the world face new terrible threats made the show into what it is. However, when really paying close attention to the story, there are some pivotal moments throughout the 15 season run that define it more than any others.

8 The Supernatural Pilot Sees Sam's Girlfriend Murdered Just Like His Mother

Supernatural Season 1, Episode 1

The Supernatural pilot is arguably one of the best opening episodes on TV. The central heroes are immediately introduced, and their differences highlighted. Together, they have a goal in finding their father, and trying to solve some monster mysteries, but nothing changes Sam's mind about his desire to return to his home and his life with his girlfriend. At this moment, the show could have seen the central characters diverge and take separate paths, but one thing changed the course of the series forever.

When Sam returns to his apartment, he searches the house for his girlfriend, but isn't able to find her at first. However, he soon discovers her body, bleeding and on fire on the roof, in exactly the same fashion that his mother died. This moment solidifies Sam's motivation to continue working with his brother, and it makes the pair more motivated than ever to track down the yellow-eyed demon responsible for decades of suffering in their family.

7 Sam Dies In Azazel's Battleground

Supernatural Season 2, Episode 21

By the end of the second season, Sam and Dean finally track down the yellow-eyed demon, but it has taken some serious sacrifices to do so. Sam spent time with a demon, refining his newly discovered demon powers due to his ingesting the demon's blood when his mother was killed. This gives Sam telepathic abilities, but it also meant he had a seriously intense temper. However, Sam is then kidnapped to become part of a game set up by the yellow-eyed demon himself.

Sam was not the first child the demon imparted his blood to, and he had gathered together a collection of these kids to compete for a chance to survive in his battleground. Despite Sam's skills as a hunter, and his gifts from the demon blood, he gets killed in the arena. However, this simply begins a trend that will become a staple in the rest of the show. Sam and Dean die a lot throughout Supernatural, but the brothers have such a strong bond and love for each other that they always find a way back, a core pillar throughout the entire series.

6 The Winchester Boys Finally Kill Azazel

Supernatural Season 2, Episode 22

The following episode, Sam is restored to life thanks to a deal with a crossroads demon and Dean, which meant he traded his soul for his brothers. However, something even more incredible happened in the season 2 finale that would alter the show's course forever once again. Dean kills the yellow-eyed demon, of course, with some help from his close. This frees up the boys from a mission that the entire series revolved around up to this point.

This moment where the biggest threat dies after two seasons was pivotal thanks to the show's ability to leave this story behind

However, it could have also left the Winchester's with no clear vision of where to go next, or what to do. Fortunately for the audience and unfortunately for Sam and Dean, the pair seem to attract all kinds of trouble simply by existing. This moment where the biggest threat dies after two seasons was pivotal thanks to the show's ability to leave this story behind, and explore new threats in a seamless way.

5 Castiel First Appears To Dean In Supernatural

Supernatural Season 4, Episode 1

Speaking of new threats, season 4 introduced some new additions that would remain vital to the series until the final season. Misha Collins plays the role of Castiel, an angel sent from heaven, who soon grows disillusioned with heaven, and who is actually in charge. While Castiel's first appearance may present him as somewhat more imposing than other seasons, he rapidly grew to become a fan favorite character and his role was expanded.

Following this, Castiel became the resident angel, who worked closely with the Winchesters and helped them to investigate new cases. Castiel is a goofball, who struggles to understand humor or sarcasm, but it makes him a perfect addition to the team. Along with his incredible powers, Castiel is entertaining and develops a genuine love for the boys. Even if the relationship gets off to a rocky start.

4 Sam & Dean Meet God, But They Don't Know It Yet

Supernatural Season 4, Episode 18

Later in Supernatural season 4, Sam and Dean encounter an unusual man who seems to have special knowledge about the boys and their adventures. Chuck is an author who has found a cult following that adores his book series, Supernatural, which is about two brothers who hunt monsters and demons. The stories are exact retellings of the boys' adventures, and obviously, they want to find out how Chuck knows all of their secrets, and why he is writing these books.

However, Chuck is not who they were expecting to meet when he opens his door in a bathrobe. The unassuming figure had no idea that the stories he was writing were real, and as becomes more clear, it appears that Chuck is a prophet. However, several seasons later, the show brings Chuck back as a pivotal part of the story, when it is revealed that he was actually God, disguising himself as an unassuming human. Chuck plays the long game, and this early introduction to a character who literally changes the course of reality was an excellent bit of foreshadowing for the series.

3 Bobby Is Brutally Killed By A Leviathan

Supernatural Season 7, Episode 10

While Sam and Dean had become intimately familiar with death, both of them having died and come back, and losing several others along the way, it was different when Bobby Singer died. John Winchester, the boys father, had struggled to connect with his sons, and he was overcome by the death of his beloved wife Mary, which led him to make choices that weren't always in the best interest of the boys. Meanwhile, John's dear friend, Bobby, became a father figure, and a beloved friend.

Bobby remained a constant source of and friendship to Sam and Dean for many years after they lost their father. Thanks to his in-depth knowledge of hunting, he was also an endless source of advice and guidance. However, when he was killed by a Leviathan in season 7, it marked potentially the most notable death for the boys since either of their parents. In the years that followed, Sam and Dean needed to find their own way, and new friends to help them, but no one could ever replace Bobby.

2 Sam & Dean Discover A Connection With The Men Of Letters

Supernatural Season 8, Episode 13

Supernatural season 8 unearths another branch of the hidden world of monsters and demons when the boys first learn about the secretive organization known as the Men of Letters. Up to this point, it appeared as though hunters were the only major group fighting the supernatural, along with some witchs who occassionally ed forces with hunters, or became hunters themselves. However, the Men of Letters were a highly educated group that found additional and alternative means to deal with supernatural threats.

Sam and Dean's grandfather had links to this group, and they were eventually led to a huge underground bunker which was full of records and technology left by the Men of Letters. This was a game changer for the Winchester's, as it meant they finally had a place to return to and call home on a more permanent basis. Instead of moving from hotel to hotel, they could return to their Men of Letters base, study the most detailed records about monsters in history, and prepare for their next big fight.

1 Mary Winchester Returns From The Dead

Supernatural Season 11, Episode 23

Finally, in Supernatural season 11, the boys have an unexpected reunion when they assist Amara, Chuck's sister, to reunite with her brother. As a way of saying thank you, Amara brings Mary Winchester back from the dead, over 30 years after she ed away in their childhood home at the hands of Azazel. Mary never got a chance to raise her boys, but when she came back to life, she made the most of the time she was gifted to see them again.

Bringing Mary back for the last four seasons of Supernatural was a major shift in the series ahead of the show ending

Mary was also a person who was just as stubborn and brave as her husband John, and she had a lot of insights to share about hunting with her grown sons. Of course, coming back from the dead was no easy task, and so there were growing pains associated with getting their mother back, but Sam and Dean were overjoyed to know that Mary was no longer lost to them. Considering the show revolves around family, bringing Mary back for the last four seasons of Supernatural was a major shift in the series ahead of the show ending.