The BBC released a synopsis for the seventh episode of Doctor Who Series 12, Can You Hear Me? :

From ancient Syria to present day Sheffield, and out into the wilds of space, something is stalking the Doctor and her friends and infecting people’s nightmares. As Graham, Yaz and Ryan return home to see friends and family, they find themselves haunted by very different experiences. Who is the figure calling from beyond the stars for help, and why? And what are the fearsome Chagaskas terrorising Aleppo in 1380? To find the answers, Team TARDIS embark on a mission that forces them to face their darkest fears.

Can You Hear Me? seems to have introduced a new species of alien, the Chagaskas.

In addition to the cast information we’ve already reported, their is a new character name, Rakaya, played by Clare-Hope Ashitey. According to dialogue overheard during location filming in cardiff, Rakaya is an alien. But is she a Chagaska?

“What do you think it feels like for them ‒ to be such tiny, ephemeral fragments of existence?,” ‘Rakaya’ was heard saying to Ian Gelder’s character during filming of the episode on Spencer Street in Cardiff on August 5.

Gelder’s character was overheard desiring to “gorge on their fear!”

Also known to be on the guest cast list:

Ian Gelder: alien
Aruhan Galieva
Nasreen Hussain: Anita Patel
Buom Tihngang: Ryan’s friend Tibo, seen in Spyfall: Part 1
Bhavnisha Parmar: Yaz’s sister Sonya Khan

The episode is written by Charlene James and Chris Chibnall. Charlene James told Doctor Who Magazine that her episode is the “stuff of nightmares.”

Directed by Emma Sullivan, Can You Hear Me? airs Sunday, February 9, at 7:10 p.m. on BBC One and 8:00 p.m. on BBC America.