For four decades, Charles Dance has enjoyed a prolific stage and screen career, but his turn as the Machiavellian Tywin Lannister on HBO’s “Game of Thrones” secured his status as one of TV’s most commanding stars. He’s now channeling that imposing energy into a slightly more benevolent — but no less intimidating — role as an alien leader on Syfy’s “Childhood’s End” (Dec. 14).

What attracted you to the role of Karellen in “Childhood’s End”?
It’s a great story, which I was not familiar with. I’ve never been a fan of science fiction, but I certainly knew that Arthur C. Clarke was the godfather of sci-fi. So when I was offered it, I read the book and then the scripts came in and I thought, “These are really good adaptations of a very good story.” To bring humanity to a character that is not human is a pretty nice challenge to have. And I’d never worked with as much prosthetic as I’ve worked with
on this.

What’s the best piece of career advice you’ve been given?
“Know when you’re being bad.” In this business, we’re surrounded by wonderful darlings, and if you can find somebody who you believe in, who has the bravery to say to you, “Listen, that was not very good,” you’re very lucky. There are very few people around who will be able to do that, for fear, rightly, of offending you or upsetting you. Because we’re very fragile creatures, actors. But I think we do need to possess that facility to be objective.

There seems to be more fantasy and sci-fi shows than ever. Why is the genre so popular?
Principally because of the success of “Game of Thrones.” You know what this business is like — something seems to be successful, let’s try to do it again and again. With the advances of CGI and all the really rather clever things we can do, we’ve now given a lie to the phrase “the camera can’t lie.” Of course it can, hugely, tell the most awful porkies.