In Series 9, "The Girl Who Died", we're introduced to Ashildr, the viking girl whose life the Doctor saved by using a Mire "Medical Kit", which will keep "repairing" her, maybe forever.

The Doctor: It won't stop, the repair kit I put inside Ashildr, not ever. It'll just keep fixing her.

Clara: Well, good.

The Doctor: I'm not sure, but it's entirely possible she has lost the ability to die.

Clara: The ability?

The Doctor: Oh, dying is an ability, believe me. Barring accidents, she may now be functionally immortal.

As the series went on, we discovered that Ashildr

effectively lived forever. Right to the end of the universe, which is still 100 trillion years away, according to some theories. The Mire medical kit kept curing her of everything, and healing every injury, not to mention that she even stopped aging.

So, why was she the only immortal? If those medical kits are used by Mire warriors, why aren't they immortal as well? Did the Doctor tamper with it? Does it only make humans, or humanoid species immortal?

  • 4
    Damn this is a good question.
    – Rand al'Thor
    Dec 29, 2015 at 19:22
  • She explicitly says she isn't the only immortal. She just happens to be the last. "Even the other immortals are gone," I believe is the line.
    – Roger
    Dec 29, 2015 at 20:27
  • @Roger That could just refer to Jack or A.N.Other, it does not mention the Mire. Timey Wimey answer could be that it only has that effect on humans
    – user001
    Dec 30, 2015 at 9:40
  • @user001 Yes, which is why this is only a comment and not an answer, but the question asked "why was she the only immortal?" I'm simply pointing out that she wasn't. I did upvote the question, because it is a good and valid question to ask. I just wanted to clarify on that one small point.
    – Roger
    Dec 30, 2015 at 13:54

3 Answers 3


Barring accidents, she may now be functionally immortal.

For all we know, they were immortal, but since they were a warrior race, "accidents" could've happened and wiped them out as a species.

That's one possibility, the other being that the kit made Ashildir immortal because The Doctor tampered with it.

Bear in mind that no explanation was explicitly given in the show, these are just a few possibilities.

  • 1
    I read an estimate somewhere that if humans didn’t die from disease or old age, we’d live an average of 1500 years before an accident killed us. Dec 30, 2015 at 13:54
  • Which makes it very hard to believe she could go 100 trillion years without having one. Maybe she did, and the Mire kit kept bringing her back.
    – tilley31
    Dec 30, 2015 at 15:32

As stated by the Doctor, Ashildr had lost her ability to die.

If you take the example of the Timelords, they could also make themselves immortal, but they didn't because of many issues. In my opinion, those main issues would be:

  • What if someone becomes something like The Master, they will cause heavy destruction
  • If they kept reproducing and didn't die, too high population
  • The rule of nature, the one who is born, has to die. I think, this have to do something with the laws of time. Even Daleks don't try to play with time. Note: Immortality is the inability to die
  • it could be an accident might resulting in wiping in the whole species. Even regeneration of a Timelord could go wrong, who knows what would happen with the immortality experiment.

The must have happened with the Mires, they were too afraid of the heavy consequences of immortality.

  • That's a good point about the "curse" of immortality. Maybe they realized about it.
    – tilley31
    Dec 30, 2015 at 15:34

There may be another explanation. I know.... it is just a theory but I think that Mire could have become immortal but I believe they did not just invented repair kit, they had tens of versions and evolution took care that it stopped work for them so they invented another version, something like antibiotics today. But Ashildir is a human, and I think it could be much simpler DNA for the repair kit to repair, and to be so much more advanced to the organism it was repairing that it could make it immortal. With Mire they had advanced DNA and overtime and versions of repair kit they developed some resistance to it.

  • 1
    Can you provide sources that might suggest your theory is correct? Perhaps quotes from the series?
    – Edlothiad
    Jun 14, 2017 at 13:50

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