1. The Ultimate Betrayal: TARDIS
The ultimate betrayal for the Doctor would be if the TARDIS killed him. Now, thinking about it, this is incredibly possible because all we've seen are pictures of the Doctor and Clara with food going into the TARDIS. Plus, from what weve seen in the Fiftieth poster, the TARDIS once again possibly blows up. This kind of treatment would make anyone resentful, especially someone she has been with for so long. Or it could even be accidental. How would we know? Unfortunately, she can't talk back to the Doctor. Someone could shoot the TARDIS or even just accidentally do something that causes the TARDIS to start producing the smoke. If the TARDIS (either accidentally or on purpose) locks them in with the bad bad smoke that we saw in "Let's Kill Hitler," they'd be pretty screwed. If they stayed in the TARDIS long enough because its crisis mode shut down the rooms,the Doctor would have to regenerate because of what the smoke did to his body. This one seems like it could happen, because it doesnt involve someone from the past coming out, it doesnt involve some big conspiracy, its a perfectly sound idea that doesnt have the Doctor going to 18th Century France in order to regenerate. It would also set the tone for Twelve, and start him off with his loss of trust in the one thing that has always been there for him: the TARDIS. Knowing Moffat, wanting to screw the Doctor out of the one thing he's always had is the perfect way to regenerate. Okay. What did I miss? What or WHO do you think is going to come back and kill the Doctor? Do you think we're gonna have a villain or radiation or Time Vortex like last time?