The White Queen

 was a fictional creature in a book written by C. S. Lewis. She was encountered by also-fictional versions of the Eleventh Doctor, Amy Pond and Rory Williams.

History
The Queen was presumably created by whoever wrote the 'Shada' book. After being transported into this book, the Doctor, Amy and Rory found her as a statue which soon came to life, chasing them. They escaped, but she followed them, managing to reach their destination years before them. The trio later arrived to find that the Queen had enslaved the natives and made it "always winter". She temporarily killed the Doctor before Amy pulled her back into the book she came from.

Abilities
She could generate lethal green energy blasts, which she shot out her hands. This was used to kill the Doctor. It may have been powerful enough to stop regeneration, though this may have been because it was written by C.S. Lewis and it is likely he didn't know about the regeneration cycle.

It is also possible that she had healing abilities as when she was first encountered, she was merely a dormant statue until she started moving again. Later, while flying through 'the space between worlds', she seemed to resemble a monstrous old woman in dark clothes. Finally, she appeared in bright white-and-blue clothing and looking young. However, it is not certain.