The upcoming episode will introduce a new menace to the BBC sci-fi series, known as The Whispermen.
"Having brought back two of the classics, the Ice Warriors and the Cybermen, this year we wanted a brand new monster to create chills in the finale," Moffat said.
"And the thought of stylish, whispering, almost faceless creatures was an idea that firstly scared me and that I thought would work well in an episode that looks forward and back."
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The showrunner also promised that 'The Name of the Doctor' will "change the course of Who forever".
"It's full of surprises and questions that have never been answered in the history of Who, including the Doctor's greatest secret," Moffat claimed.
"We'll also find out what makes his new companion [Clara, played by Jenna-Louise Coleman] so impossible and there's a surprise that no-one has got right so far."
Coleman previously appeared on Doctor Who as spacefaring Oswin and Victorian governess Clara, with the Doctor attempting to unravel the mystery of her multiple identities in recent episodes.
Hinting at what to expect from the finale, Coleman teased: "All I can say is that Clara hasn't just met the Doctor three times before."
Doctor Who continues tonight at 6.30pm on BBC One with new episode 'Journey to the Centre of the TARDIS'.
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Watch a preview of tonight's Doctor Who episode below: