Doctor Who star Peter Capaldi has said his regeneration as the Time Lord will be "more complicated than recent ones".
The actor will step down from the role after the Christmas special and another actor is expected to take his place, but Capaldi has said it will not be an easy process.
Show boss Steven Moffat and Michelle Gomez, who has played the villainous Missy since 2014, will also leave the show.
He told Radio Times: "I can't go into the details. I know what happens, but I don't know how it happens. Certainly it's not straightforward. It's more complicated than recent ones.
"That's one of the appeals of being in the show - it has death at the heart of it. He's the only hero on TV who dies again and again."
The former star of The Thick Of It announced he would be stepping down from the role of the Doctor earlier this year because he fears he would not be able to keep it fresh.
He said: "I love this show, but I've never done anything where you turn up every day for 10 months.
"I want to always be giving it my best and I don't think if I stayed on I'd be able to do that.
"I can't think of another way to say 'This could be the end of civilisation as we know it'.
"With episodic television of any genre, the audience wants the same thing all the time - but the instinct that leads the actor is not about being in a groove."
:: The full interview is in Radio Times, which is on sale now.
Moffat has said he is focused on giving Capaldi a "grand, several-stage finale".
He told the magazine: "I'll strike a balance between not revealing spoilers and trying to get people to watch. I'm honour-bound as a writer not to give a damn about my departure.
"There's no story about me leaving, the kids don't know I exist - you can't really get me away from the balcony when nobody knew I was in the building.
"But it's about giving Peter a grand, several-stage finale and trying to refresh the story that Doctor Who gets involved in with a tremendous crisis, during which he gets in some way mortally injured and has to turn into another actor."
He jokingly backed himself as Capaldi's successor, saying: "I think it should be me. That would be awesome. It's about time they let a writer play the lead. I mean, I've been making up everything he says for years, so I can totally do it."