5. The Celestial Toymaker
The Celestial Toymaker is a powerful immortal being whos just become a bit bored of his own agelessness, really. So hes done what wed all do go quietly mental while seeing what we could get away with. To this end, he dresses as a Mandarin and builds an entire fantasy world based around his love of playing games. Its this world that William Hartnells Doctor steps into during the shows third season, and the Toymaker just hates to lose, seemingly a bit of a deal-breaker if youre the universes living embodiment of games and illusions. However, all villains need a motivation and a strangely rigged gaming world which you must surpass to keep your freedom would work extremely well as a standalone episode. Make no mistake, I dont think the Toymaker could keep appearing in a season-straddling primary antagonist role like the Daleks, the Cybermen, the Master, Davros or the Great Intelligence, but as an occasional villain like the Weeping Angels, theres a hell of a lot you can do with the set-up, especially when youve got writers like Neil Gaiman, Toby Whitehouse and Steven Moffat on board theyve literally got a whole toybox worth of things to work with, and Id love to see what they think up.