Clara Oswald is one of the Doctor's most extraordinary companions. In order to help the Doctor she allowed the time winds to tear her into countless different iterations of herself living and dying all over time and space, like echoes. The Eleventh Doctor initially encountered two of the 'echo Claras' and was mystified by them. He named her the 'Impossible Girl' and resolved to find her, eventually tracking down the 'real' Clara to modern day England. The Doctor finally discovered the truth about Clara on Trenzalore and was able to save her from the threat of the time winds. He brought her safely back to Earth where she began a job as a school teacher and she was present when he regenerated in into his twelfth incarnation. Since then they have gone on countless adventures together.