10 Oldest Characters In The Doctor Who Universe

Estimated Age: Almost 100 trillion years.

Despite only appearing in a few episodes in Series 9, Maisie Williams' Ashildr went on one hell of a journey.

Introduced as an ordinary Viking girl living in the 9th century, she encountered the Twelfth Doctor and Clara Oswald, and helped them battle a warrior race called the Mire. Ashildr was killed during this battle, but the Doctor brought her back to life using Mire technology - and this is the reason she earned the top spot on our list.

That technology didn't just bring her back to life - it made her immortal. The next time we see Ashildr, she's been alive for centuries, but even still, that's only the beginning portion of her life: she lives throughout the 21st century, and then on and on and on, until she winds up at the literal end of the universe. In case it wasn't obvious, that's an unfathomable amount of time away.

It's hard to pin an exact date on when the end of the universe takes place, but in Series 3's Utopia, the Tenth Doctor notes that it's around the year 100 trillion. So, if we go with that, then this makes Ashildr almost 100 trillion years old.

Not bad for someone who still looks like a teenager!