The Doctor Whoniverse just expanded.

Disney Branded Television and the BBC have made official at San Diego Comic-Con that The War Between the Land and the Sea will extend the world of the British science fiction TV series with a focus on the 1970s foes, the Sea Devils.

Confirming long-running speculation by Whovians, Disney and the BBC revealed the five-part series will star Russell Tovey and Gugu Mbatha-Raw, alongside returning Doctor Who cast members Jemma Redgrave, as Kate Lethbridge-Stewart, and Alexander Devrient as Colonel Ibrahim. 

The official synopsis reads: “When a fearsome and ancient species emerges from the ocean, dramatically revealing themselves to humanity, an international crisis is triggered. With the entire population at risk, UNIT steps into action as the land and sea wage war.”

“There’s a race that lives beneath the oceans,” Doctor Who showrunner and executive producer Russell T Davies said about the Sea Devils during the Comic-Con panel. “It’s war on an epic scale, and it’s got a tremendous cast.” He also noted about Tovey and Mbatha-Raw: “They have both been in Doctor Who before, but they’re not playing the same parts.”

The series comes as Disney and the BBC look to rival the Marvel Cinematic Universe with a spinoff created by Davies. “I’m so lucky to work with such a magnificent cast. And this is a huge, muscular, thrilling drama which will shake The Who universe to its foundations. When the Doctor’s not in town, the whole of humanity is in trouble,” Davies said in a statement.

He wrote the spinoff with Pete McTighe (A Discovery of Witches, The Pact, Doctor Who). The War Between the Land and the Sea also promises the return of the Sea Devils, classic Doctor Who villains first seen in 1972.

Filming on the spinoff series will start next month, with Dylan Holmes-Williams directing. There’s no word on a premiere date, but the series will air exclusively on Disney+, where available internationally, and BBC One and BBC iPlayer in the U.K. market.

The War Between The Land And The Sea is produced by Bad Wolf, with BBC Studios for Disney Branded Television and the BBC. It also the latest season of the BBC’s hit science-fiction series Doctor Who launching on Disney+ and the BBC, with Ncuti Gatwa (Barbie, Sex Education) starring as the Fifteenth Doctor and Millie Gibson as his traveling companion Ruby, 

Besides Davies, the executive producer credits for the spinoff series are shared by Phil Collinson, Joel Collins, Julie Gardner and Jane Tranter.