Peter Capaldi has announced he’ll be leaving Doctor Who, presumably at Christmas 2017. Although the teaser for season 10 has shown the Doctor’s hand glowing with regeneration energy, suggesting an earlier regeneration (or at least the start of one), season 10 is complete and there is not yet any casting announcement on Doctor 13.
But perhaps most important is “How”. The Doctor’s regenerations are-traditionally-caused by physical trauma or aging, with two exceptions. Here’s a run-down:
- Old age
- Forced by the Time Lords
- Radiation sickness
- Fall from great height
- Poisoned by toxic exposure
- Head trauma (although it’s not really made 100% clear
- Shot and then hearts attack
- Forced via drinking potion designed to turned him into a Warrior
- (War) Old age, or perhaps just having fufilled his purpose
- Time vortex radiation
- Radiation again, although he ‘wasted’ a regeneration turning back into himself when shot by a Dalek earlier on.
- Old age, and this would’ve been the final death of the Doctor had the Time Lords not given him regeneration energy to get a new cycle.
There’s certainly been some variety to the regenerations-pretty much all the new series regenerations have had the Doctor standing up, pulsating with glowing energy and then morphing into his new self. It’s different, but it also helps mask any flaws with the morphing effect.
The most unusual regeneration however, was probably from the fourth to the fifth-in which a mysterious figure, the Watcher-merged with the Doctor to help with the metamorphosis.
As for how he’ll go, the Doctor’s regenerations are often caused by some form of self-sacrifice to save the world, universe, or in perhaps some of the best cases-just his companions, as was the case with Peri and Wilf.
So we’ll see how if that happens. While the Twelfth Doctor originally started out fairly selfish, in the next season he braved being stuck in a time loop for billions of years and once again losing the respect of his own people to save his companion Clara from pretty much certain death.
There’s also one other factor that’s been involved in a few of the Doctor’s regenerations-the Master has been present for quite a few of them.
In Logopolis, his actions result in the Doctor falling off a satellite dish to his “death”. In the Caves of Androzani, he appears as a hallucination asking the Doctor to die. In the TV movie, his sabotage of the TARDIS causes an emergency crash landing that leads to a series of events, that leads to him regenerating-and the End of Time he leaves the nuclear-powered gate running, which the Doctor absorbs the radiation of to save Wilf.
And of course this particular Doctor has been tied with the Master since his very first episode: “Deep Breath”. In particular, Missy. So maybe the Mistress-or even her predecessor (John Simm) will once again have a role in this Doctor’s demise.
There’s a few other things to consider as well. In the episode “Witches’s Familiar” The Doctor’s regeneration energy is stolen by Davros, and this might somehow complicate things down the line.
Plus there’s the mystery of just when he goes to Gallifrey during the Time War to help save it with his earlier selves, as seen in his “Day of the Doctor” cameo/first appearance. Perhaps this is one of his final acts?
and finally, The Valeyard-from the classic series “Trial of a Time Lord”-who is supposed to be an evil version of the Doctor somehow created from the Doctor’s dark side somewhere around this point in the Doctor’s life-ever be explained, or somehow be involved?