Peter Capaldi will be returning for the last time as the twelfth doctor of BBC's long-running series "Doctor Who." When the series returns with all-new episodes, viewers will come across new and old-school monstrous characters.

Like Capaldi, the upcoming season will be "Doctor Who" executive producer Steven Moffat's last run in the series. Before Moffat can formally depart from the show, he expressed his excitement about the installment, especially for the monsters. A few of these monsters are the Ice Warriors and the Mondasian Cybermen.

According to him, viewers will come across a serpent that "lives under the Thames in the shape of the Thames which, now that you realize it, the EastEnders title sequence has always clearly been about a giant snake."

Moffat also mentioned small and cute creators that "communicate by emojis." These Emojibots, however, should not be trifled with, as they can turn one into a skeleton.

The exec shared that the most hair-raising creatures will be shown in an episode written by Mike Bartlett. He held back the details about the monsters, but he did guarantee the episode's authenticity. He said that it will be one of those moments when an individual cannot help but scream out "UGH!"

Furthermore, Moffat admitted that new antagonists will be making their way to "Doctor Who." Again, he kept his lips shut, and he referred to them as the Monks even though this is not really their given name on the show.

Mirror reports that Capaldi's decision to quit the show comes from his struggle to keep things interesting. Capaldi's replacement has yet to be revealed. Meanwhile, showrunner Steven Moffat will be replaced by Chris Chibnall.

Joining Capaldi this season is Pearl Mackie, who will be the Doctor's newest companion Bill. Matt Lucas will also be reprising his role as Nardole.

"Doctor Who" will debut on BBC America on Saturday, April 15.