Steven Moffat's 10 Greatest Additions To Doctor Who

Few show-runners get the chance to believably alter series lore, but Moffat managed to do so with the introduction of the War Doctor, a previously unknown incarnation of The Doctor.

First seen in 'Name Of The Doctor' as a shadowy figure in The Doctor's time stream, 'Day Of The Doctor' reveals him as the incarnation who fought during the Time War. He is initially rejected by his Tenth and Eleventh selves as being 'the one who broke the promise'.

Thankfully, events transpire to reveal that The War Doctor actually helped all of his past, and future incarnations save Gallifrey from destruction by locking it in a single pocket of time. The other Doctors come to view him much more kindly as a result.