The first female Master could have been a disaster but instead audiences were given something very special indeed. There had been talk about whether the Doctor could ever regenerate into a woman, so perhaps it was a clever step by Steven Moffat to try out the gender-regeneration trick with his nemesis instead. It worked. Michelle Gomez's delivered a Master - or Missy - that was evil, psychotic, manipulative and a true thorn in the Doctor's side. Her introduction was an intriguing one. Was she a regenerated River Song? Romana? Or the more obvious Rani? Even an older Clara was touted before she finally revealed herself to the Doctor in Dark Water. A dark mirror to the already darker Twelfth Doctor, she made her mark in the Series 8 finale, bantering with the Doctor like a deranged Mary Poppins, murdering everyone in plain sight - including poor Osgood - and enslaving human corpses just to give the Doctor the army he needed to rid the universe of everything that was evil. Missy and the Doctor's relationship was sick, twisted and perfectly captured the love/hate relationship that defines them. Gomez has amazing chemistry with Peter Capaldi and it is easy to see why she will be making her return in Series 9. Because nothing keeps the Master down for long - not even her supposed 'death'.