While doing loads of press for his role in Star Trek Into Darkness (in theaters this Thursday in the U.S.), Benedict Cumberbatch spoke about creating the dragon Smaug in Peter Jackson’s second The Hobbit film.

Being able to portray Smaug in the Middle Earth franchise is a huge opportunity and “full circle moment” for Cumberbatch because J.R.R. Tolkien’s iconic creature was the first dragon he was introduced to as a child. “My dad read the book to me and it was a bedtime treat if I had done well,” the actor told Speakeasy. “If I had been a good boy, I’d get two chapters as opposed to maybe one or none if I had been really bad.”

The actor holds a detailed vision of Smaug. “This incredibly vainglorious, beautiful, fantastical creature of myth with such power and human frailty, his vanity and self-promotion and ego being his own self-destruction really, and not realizing his weakness and his strength, and having a literal Achilles heel — it fascinated me.”

Cumberbatch also told a quick story of how he ended up doing motion capture to animate the dragon even though Jackson didn’t need it.

“He wasn’t that in need of [the motion capture] but he said, ‘do you want to do it?’

I said, ‘Absolutely, I do. That’s the great appeal, trying to bring this –’

He said, ‘But–’

I went, ‘I know what you’re going to say: I’m a biped mammal, I’m not a serpent with tiny claws or legs. I don’t have a tail, I can’t breathe fire or fly, and the rest of the things that aren’t dragonlike about me. But I do think in my imagination I’ve got something which might at least push the WETA animation into a direction.’

He went, ‘Come down and play.’”

Our only official look at Smaug so far came at the very end of The Hobbit: An Unexpected Journey when we saw the dragon open its eyes. However, this past weekend we saw a dragon model appear in a theater usually reserved for Jackson memorabilia, and some fans have speculated that it is a new look at Smaug.

The second film in The Hobbit trilogy The Desolation of Smaug opens in theaters December 13.