Fans had feared the worst for a while now, and earlier this week those fears were confirmed: 2017 is the final year for Peter Capaldi's tenure as the star of Doctor Who, the much-loved British TV show about an eccentric alien time traveler. Veteran Who fans are used to this changing of the Tardis guard—bringing in new Time Lords is essential to the show's appeal—but Capaldi's Twelfth Doctor had something special, something Whovians will miss with a mad intensity.

For one thing, I was looking forward to seeing more of how Capaldi's portrayal would grow and deepen over a few more years in the role—not to mention, getting to see more of his Doctor interacting with companions other than Clara Oswald (Jenna Coleman), who departed last season. (Pearl Mackie's Bill is set to debut when the show returns in April.) But that's just the surface stuff. What Capaldi brought to the Twelfth Doctor was a mix of depth, humor, and vulnerability that captured the best of his predecessors' performances—but also added something new and radically brilliant.

The Doctor with a Thousand Faces

The ever-changing image of Doctor Who embodies a wild paradox: The Doctor is one of the most recognizable characters in all of pop culture, but he's also one of the most versatile. (Though up to now, he's always been a white guy.) The Doctor can be a grumpy old codger, a Harpo Marx-faced bohemian, or a youthful college professor—and if you don't like one Time Lord, just wait a few years, and everything will be different again.

Peter Capaldi's approach to playing the Doctor felt brand new in vey crucial ways. And whoever takes over the role after Capaldi, he or she will be able to explore the new territory he found.

But even as the Doctor has transformed over the years, every actor has left something of himself behind in the character. The mercurial Patrick Troughton was the first actor to create a new version of the Time Lord after original star William Hartnell, and Troughton's performance has proved something of a touchstone for several Doctors, especially Peter Davison and Matt Smith. But you can see every Doctor drawing on his predecessors, while adding brand new grace notes for his successors to pick up on. That's certainly what recent Doctors Christopher Eccleston, David Tennant, and Matt Smith did as they built a new 21st century template for the Gallifreyan hero.

Who in the Time of Capaldi

And yet, Capaldi's approach to playing the Doctor felt brand new in vey crucial ways. Sure, he conspicuously channeled 1970s mainstays Jon Pertwee and Tom Baker at times, along with his immediate predecessor Smith. But he also seemed to find new places to take the character, new avenues in both time and space. And whoever takes over the role after Capaldi, he or she (a woman Doctor, wouldn't that be nice?) will be able to explore the new territory they found.

Let's take time first—Capaldi's reign as the Doctor has famously seen a different rhythm than either of his predecessors. Capaldi preferred longer scenes, and fewer quick, breathless sequences, which head writer Steven Moffat seemed happy to accommodate. This culminated in stories like 2015's "Zygon Inversion" and "Heaven Sent," in which Capaldi carried long stretches of time with dramatic monologues. The lengthy anti-war speech in "Zygon" stands out, even amongst all the other great speeches the Doctor has given over the years, for its weight and emotional range.

Add to that the comic timing that the Twelfth Doctor displayed, which was markedly different than Smith's amiable slapstick. Capaldi's Doctor was more willing to be the butt of an extended joke, marinating in wounded vanity when confronted with the real-life Robin Hood (in "Robot of Sherwood") and a River Song who mocks him behind his back ("The Husbands of River Song"). And yet, his Doctor's laughable amour-propre was capable of flipping to a deep vulnerability and a deep tenderness. Seriously, watch the scene where the Twelfth Doctor finally shows his true identity to River Song, in the middle of one of her tirades—it'll rip your heart from your chest.

(And just as Capaldi's Doctor is able to be the butt of running jokes to a greater extent than his predecessors, he's also able to be on the receiving end of more sustained and harsher criticism, particularly from Clara's boyfriend Danny Pink, without forcing the audience to take sides.)

And then there's space. Going into the role, Capaldi had a couple of major advantages—first, he was getting to play a version of the Doctor who'd been freed of the guilt of the Time War, which had weighed down all three of his predecessors in the new version of the show. But also, he had a fine template for how to play a version of the Doctor who had lost too much and yet kept up an impossible bravado in spite of everything—thanks to Matt Smith's wounded-and-spritely turn. But nevertheless, Capaldi turned everything I expected from Doctor Who on its head. To Smith's brooding whimsy, Capaldi added a whole host of mannerisms: twitchy eyes, a slight hesitation before making any bold statements, a thin smile, and too many others to name.

Capaldi's Doctor not only seems ancient and emotionally damaged, but also aware of his own contradictions. He's still utterly perplexed by human beings and our baffling emotions—but you can also see him calculating his next move and manipulating situations, all with more low cunning than we've seen since Sylvester McCoy's version in the late 1980s.

The Twelfth Doctor's Final Year

Most of all, Capaldi's Doctor has evolved and revealed more layers as his long-running relationship with Clara has deepened. The main arc of Capaldi's first two seasons involved not a villainous scheme or a cosmic mystery, but rather a human, character-based storyline. We saw the Doctor attempting to convince Clara that he wasn't a monster—and in the process, turning her into a bit of one. For this storyline to work as well as it did required a whole battery of subtle cues from Capaldi about the stew of arrogance and self-doubt that the Doctor marinates in.

It's looking as though Capaldi's final year as the Doctor will see lighter storylines and less gloom, thanks to his new companion, Bill. That's probably a good thing after the intense darkness of stories like "Face the Raven" and "Heaven Sent." Based on what Capaldi and Moffat have said in interviews, Capaldi's final set of episodes will show just how funny his adventures can be. The Twelfth Doctor now has 12 episodes (and a Christmas special) with which to add every last bit of dramatic flair he can, giving his successor a wealth of traits and ticks to inherit. But no matter what Season 10 brings, Capaldi will have taken the Time Lord to places he had never gone before—and no amount of regeneration will be able to change that.