As Peter Capaldi’s last appearance as the Time Lord, many fans would expect the episode to be an emotional but joyous one.
The instalment has all the compartments to create a happy atmosphere as the Doctor will be reunited with his companion Bill Potts (played by Pearl Mackie) and will also meet up with the first ever Time Lord (David Bradley).
However, Steven teased the special will be a lot more sinister than previous years when he spoke on the panel at the London Screenwriters’ Festival.
When asked how he and Sherlock co-creator Mark Gatiss have balanced the detective’s selfish tendencies with his good nature, the writer spoke about the Doctor in comparison to reluctant hero Sherlock and Superman.
He said: “Why would Superman be good? Because kindness stops you being lonely, would be the answer. That’s what that’s about, for Sherlock Holmes.
“He’s good because for all he protests about it, there are people he cares about. So, kindness is what makes a unit of us.
“So if you are sane and rational, kindness is by far the best path. There isn’t anything rational about being vile and awful and evil. It’s not actually a good strategy.”
He cryptically added: “Prepare for that to be contradicted on Doctor Who on Christmas Day…”
Despite Steven’s warning, Peter recently revealed his last scene when he regenerates into the new Time Lord, Jodie Whittaker will be poignant.
Talking about the emotional moment, the actor told Digital Spy: “I felt Steven [Moffat] had written something very beautiful, and very right for my Doctor, so I was just happy to try and do my best with it.”