After the buoyant, uplifting ending of “The Day of the Doctor” in 2013, Doctor Who took a darker turn almost immediately. While Matt Smith’s era was characterized by much of the same relentlessly boyish charm as the first David Tennant era, Who shifted into more mature territory once Peter Capaldi emerged as the 12th Doctor. In his first season (2014’s Season 8), the 12th Doctor was moody, impatient, and disinterested in proving that he was a nice guy. But, throughout the season, the 12th Doctor was just as heroic as his previous incarnations, albeit a bit snarkier about it.
But the one thing the Doctor didn’t have during the Matt Smith era was a new version of the Master, and with one brilliant twist, in its two-part Season 8 finale, 10 years ago, Doctor Who changed the possibilities for who and what a Time Lord could be, forever.
