I still don't really understand what happened at the end of series 7 when John Hurt made his first appearance.
John Hurt's Doctor was a regeneration inbetween Eight and Nine that The Doctor later refused to acknowledge, given that he came into being in the midst of the Time War, committed mass genocide by wiping out Gallifrey and the Daleks (ending the Time War) and refused the title "Doctor". This was covered in The Day of The Doctor and its prequel, The Night of The Doctor (where we see Eight regenerate into Hurt).