Since the first season of the revitalized series, Steve Moffat held the crown for writing the scariest episodes.

"The Empty Child" was a thriller, and "Blink" is still amongst the most terrifying episodes of the series … but now he has a new villain to top them all.

Known only as The Silence, the new monsters will play a big part in the sixth season when it premieres later this month

"I think The Silence are one of the greatest monsters of recent years," Smith said, according to Digital Spy. "[They are] certainly one of the scariest. They're also very clever and I love the fact they've been silently working since the dawn of time to make The Doctor come unstuck."

Not only are they scary, but Karen Gillan (who plays Amy Pond in the series) believes they "actually rival the Weeping Angels in terms of scariness."

In the tail end of the fifth season The Silence were briefly teased with the words "silence will fall" echoing through the Tardis ... and silence will be falling for one of the main characters on the series.

It has already been teased that the first episode of the new season -- entitled "The Impossible Astronaut" – will feature the death of a major character on the show as The Doctor and co. head to the United States for a special mission from The White House.

Also making an appearance in the sixth season are the Cybermen, who are expected to go up against the Doctor and his old roommate (James Corden). According to The Metro, both Corden and Smith have been seen brandishing a cybermat - a weapon of the Cybermen.

Meanwhile, former "Firefly" and "Battlestar Galactica" actor Mark Sheppard has revealed that he has completed his guest appearance in season six of the series. He will play a character named Canton who will be appear in what is being described as the shows fall premiere. Unlike other seasons, "Doctor Who" will run for 7 weeks and then take a summer vacation before returning for the final 6 episodes in the fall.

Sheppard will be appearing in the first two episodes in the final run of episodes.

"Doctor Who" returns to BBC1 in the United Kingdom and BBC America in the United States on April 23.