10 Doctor Who Villains You're Surprised Only Appeared Once
9. Eternals
'Enlightenment' is one of the best Peter Davison serials. Taking place during an intergalactic yacht race, it introduces the Eternals, god-like beings that play games with dispensable human pawns (or Ephemerals) for prizes. The Doctor is rightly horrified, and his confrontation with Striker gives Davison some of his best material in the role.
The Eternals have been mentioned in passing throughout the new series, but haven't yet made a return. Or at least, not explicitly. In the Thirteenth Doctor adventure 'Can You Hear Me?', the TARDIS team come up against Zellin who can manifest people's fears and do weird things with his fingers. He tricks the Doctor into freeing his lover Rakaya but is, of course, eventually defeated.
While not explicitly referenced as Eternals on-screen, a tie-in story entitled 'The Guide to the Dark Times', was published in the Official Doctor Who Annual 2021. Written by River Song, it outlines the history of the mythical dark times, and suggests that Zellin and Rakaya were Eternals. Regardless of whether this was the intention of the original script, a Doctor Who story that tackles gods who treat human beings as toys would be fantastic.
It's a regular fallback plot across the Star Trek series, so isn't it time that the Doctor had their own Q?