Fantasy TV shows can change quickly, and when big plot twists and narrative changes are written into the story, they have a major impact. The magic systems and rules of the realities that these fantastical worlds exist in allow the writers and creators to experiment with story and character dynamics, leading to episodes that change everything for the series. These episodes typically incorporate a tone shift and switch the show's focus to a new set of character dynamics. Altering a series so drastically can either save and prolong its run or be the beginning of the end for the show.

The fantasy TV shows that deserved more seasons rarely get the chance to reinvent themselves and adapt to significant change. However, a long-running series must quickly adjust when actors decide to leave the show or a detailed story arc has reached its end. While it can be daunting to take on the challenge of changing a series drastically, it's also an opportunity to start fresh and explore new facets of the story. Depending on when these pivotal episodes occur, either the beginning or end of the show, this will often determine how the audience reacts to the unexpected new direction.

10 The Rains Of Castamere - Game Of Thrones (2011–2019)

Season 3, Episode 9

Since the beginning, Game of Thrones was a TV show where no one was safe, and audiences had grown used to the main characters being killed off all the time by the end of season 3. However, this doesn't make it any less shocking or devastating when it happens, especially to characters who were set up to be vital parts of the series. While book readers were aware that the tragedy was coming, "The Rains of Castamere" remains one of the most unexpected twists in the series.

Despite the surprising events of the episode, it's still considered one of the series' best, and the direction Game of Thrones took after this was better for the show.

Up until this point, Robb Stark was one of the biggest threats to the Lannisters' claim on the Iron Throne, and The Red Wedding was the event that ended the unification of House Stark until the final season. Despite the surprising events of the episode, it's still considered one of the series' best, and the direction Game of Thrones took after this was better for the show. After The Red Wedding, Game of Thrones narrowed in on the remaining storylines and focused on the mysteries outside the Seven Kingdoms.

9 I’m Thinking Of You All The While - The Vampire Diaries (2009–2017)

Season 6, Episode 22

Nina Dobrev's performance as Elena in The Vampire Diaries defined the show for the first six seasons, as she was the center of the love triangle and the character that almost every plot revolved around. However, Dobrev eventually left the show, and the series creators had to think of a way for Elena to disappear while keeping the show going. In The Vampire Diaries season 6 finale, "I'm Thinking of You All The While," Elena is put under a curse and is put into a magical sleep for the remainder of the series.

It was a surprising turn of events, and unfortunately, The Vampire Diaries became a fantasy TV show that went on for too many seasons after Dobrev left the series. The series had been declining in quality before this, as the plot lines were becoming even more outlandish and slightly repetitive. However, without Elena, the series lost a central part of the enduring conflict and created a vacuum that the show wasn't ready to fill. Though Dobrev made an appearance in the series finale, it was difficult to sustain interest in The Vampire Diaries without her.

8 The Gift - Buffy The Vampire Slayer (1997–2003)

Season 2, Episode 22

Throughout Buffy The Vampire Slayer season 5, Buffy ponders what it means when the spirit guide tells her, "Death is your gift." Initially, she believes this to mean that the physical prowess and slaying of demons is all she offers to the world: that she's merely an agent of death. In the Buffy season 5 finale, she understands the sacrifice she makes to save both Dawn and the entire world is her true gift, enshrining her as a paragon of heroism and selflessness. However, the death of the protagonist usually heralds the conclusion of a series.

While audiences were somewhat surprised at the serious and dark nature of Buffy season 6, this switch-up was what the series needed to justify two more installments.

Part of the reason Buffy season 5 had such a dramatic finale was because the show was officially canceled on the WB and moved to UPN for seasons six and seven. While audiences were somewhat surprised at the serious and dark nature of Buffy season 6, this switch-up was what the series needed to justify two more installments. The Buffy who comes back from the grave isn't the same person who left Earth, but this gave Buffy The Vampire Slayer the opportunity to evolve into an adult show and shake off its high school roots.

7 A Curious Thing - Once Upon A Time (2011–2018)

Season 3, Episode 19

Regina and Emma are two of the most important characters in Once Upon A Time, as they work well as foils, being the Evil Queen and the Savior, and have great onscreen chemistry. In season 1, Regina is inarguably the antagonist, as she casts the curse that condemned the residents of the Enchanted Forest and will do anything to keep Emma away from Henry. This culminates in Emma breaking the curse by kissing Henry on the head, which is true love's kiss thanks to the mother-son bond they've developed.

This moment comes full circle in the season 3 episode "A Curious Thing," as the roles are finally reversed, and Regina is the one to break the new curse with her own true love's kiss, as she has become a selfless mother to Henry. Finally, Regina can fully accept herself as a hero and a Savior and stop thinking of herself as the Evil Queen. Her actions also prove this to the people who doubt her and show Henry that she puts him above all else. The show could then focus on developing other villains.

6 Through The Looking Glass - Lost (2004–2010)

Season 3, Episodes 22 & 23

Every season finale of Lost proved to be even more explosive than the last, but the season 3 finale, "Through The Looking Glass," set the show on track for the trajectory of the final three seasons. Lost fully delved into the supernatural elements of the island and incorporated even more experimental storylines like time travel, the flash sideways, and the growing rivalries between Jack and Locke for the remainder of the show.

"Through The Looking Glass" includes two of the biggest reveals of the entire series.

"Through The Looking Glass" includes two of the biggest reveals of the entire series. Charlie reveals that the incoming ship is "Not Penny's boat," and the audience discovers that the flash sequences in season 3 haven't been of the past but of the future with Jack's statement, "We have to go back." The audience could never look at the flash sequences the same way again, and though it became certain that the survivors had left the island, the nature of its secrets grew even more mysterious.

5 No Better To Be Safe Than Sorry - The Magicians (2015–2020)

Season 4, Episode 13

The audience first meets Quentin Coldwater, played by Jason Ralph in the first four seasons of The Magicians, as a lonely and misunderstood young man searching for meaning. He finds this through his discovery of his propensity for magic and ittance to Brakebills University, which sends him on quest after quest. Though The Magicians is a mystical series, it also blends elements of horror and plenty of darkness into the narrative, with tragedy striking as often as the heroes triumph.

With every season, Quentin becomes more sure of himself and his magic, and by The Magicians season 4 finale, there was little left to do with Quentin's character than complete his narrative arc. This leads to Quentin making the ultimate sacrifice for his friends and leaving the series for good. Though there was only one season without Quentin, The Magicians is almost unrecognizable without him. However, the series did justice to his legacy by leaning into the stories of the remaining characters.

4 To Kill The King - Merlin (2008–2012)

Season 1, Episode 12

The dynamic between Merlin and the woman who would come to be his nemesis, Morgana, is markedly different in season 1 than it is by the end of Merlin. For most of the series' first outing, Morgana seems like an ally and friend to Merlin, but in the season 1 finale, "To Kill The King," Morgana begins to show her potential for evil. What begins as her quest to save Gwen's father from being executed by Uther soon turns into her aligning herself with dark magic and turning away from the side of good.

From here on, Morgana and Merlin are on parallel journeys that will inform the remainder of the series and see their fates intertwined.

It's a nuanced issue, as Uther and his hatred and fear of magic have made him into a tyrant, but he's still Arthur's father, and Merlin knows that using dark magic is wrong. He must unpack what he wants to do next, and it's the first time that Morgana and Merlin are properly at odds, but not the last. From here on, Morgana and Merlin are on parallel journeys that will inform the remainder of the series and see their fates intertwined.

3 Swan Song - Supernatural (2005-2020)

Season 5, Episode 22

Initially, Supernatural was written to have a tight five-season-long arc, and this is clear based on the events of the season 5 finale. "Swan Song" was the culmination of the ongoing battle the Winchester brothers had with the demon Azazel, who killed their mother, and their defeat of Lucifer after he took control of Sam's body. Though they successfully prevent the apocalypse, it's not without great cost, as Sam is changed by this experience forever.

Supernatural changed a lot between seasons 1 and 15, and one of the biggest narrative shifts after the conclusion of season 5. Of course, some of the show's best storylines occurred after season 5, and the more comedic and action-oriented slant that the writing took after this worked in the series' favor. When the show picks up with the season 6 premiere, things are different, and the dynamic of the brothers must be rebuilt as the show finds its footing once again and delves even deeper into the world's lore.

2 The Wedding - Outlander (2014–Present)

Season 1, Episode 7

When Claire first gets transported back in time to 18th-century Scotland, she isn't ready to embrace her new life, let alone look for love and ion. However, it doesn't take long for Jamie, the kind and sensitive hero she meets not long after arriving there, to become much more than her ally. For a variety of political reasons, the pair are compelled to get married, and Claire is no longer pining for her life in the 1940s. This is the turning point of Outlander season 1 when Claire commits to her fate.

From here on out, the entire series revolves around the romance between Claire and Jamie and sees them cross time and continents to be together.

Additionally, this episode marks the beginning of the steamy scenes that Outlander quickly became known for, thanks to the chemistry between the actors who play Claire and Jamie, Caitríona Balfe and Sam Heughan. From here on out, the entire series revolves around the romance between Claire and Jamie and sees them cross time and continents to be together. While their love story isn't always happy, this blissful moment of their wedding day is a seminal moment in the show.

1 I Smell A Rat - True Blood (2008–2014)

Season 3, Episode 10

Though the romance between Bill and Sookie is the inciting incident in True Blood, her chemistry with the dark and mysterious vampire Eric is just as much of a driving force in the series. Their building dynamic finally comes to a head in "I Smell A Rat," which sees Eric and Sookie kiss for the first time, which is a huge moment in the show, especially because Bill and Sookie had been trying to build a relationship. However, this isn't the only reason this episode is so important.

It was always clear that there was something different about Sookie, as she could read people's thoughts and had an affinity for supernatural creatures. In "I Smell A Rat," she finally discovers the reason for her abilities, and everything comes together when Bill reveals that she's part faerie. This is the reason her blood lets Bill walk in the sun and changes Sookie's perception of herself and the supernatural world. After this episode, she must reevaluate her feelings about herself and the many vampires in her life.