When we first meet her in Series 4 River Song dies sacrificing herself to save the Tenth Doctor, his companion Donna Noble and the rest of the inhabitants of The Library. Later it is revealed that River Song has the ability to regenerate. There are two reasons why River Song did not regenerate in The Library.
- The death she dies was fatal to Time Lords. In The Library, the Doctor had initially planned for himself to take the seat that would prove fatal. He planned that expecting to die.
- In Series 6 we learn that River Song while capable of regeneration give all of her remaining lives to revive the Doctor after she had poisoned him. Thus by the events of The Library she had no more lives left.
- It's also quite possible that River Song intentionally killed herself now that she had progressed to the point where the Doctor could no longer know her. This is forshadowed in "Day of the Moon" when she tells Rory that she knows that a time will come when the Doctor won't know her at all, and she believes that will kill her.
See Also Edit
- Who is Professor River Song* What is a Time Lord
- How many lives did River Song have
- Can River Song be resurrected like the others who were saved in The Library