During the "Into the Whoniverse" panel at San Diego Comic-Con on Friday, fans of the beloved sci-fi series were thrilled to learn about the expansion of the "Doctor Who" universe with a brand-new spinoff. The five-part series, titled "The War Between the Land and the Sea," will feature a star-studded cast including Russell Tovey and Gugu Mbatha-Raw.

Russell Tovey, known for his roles in "Feud" and "American Horror Story: NYC," and Gugu Mbatha-Raw, recognized for her work in "Surface" and "Loki," will lead the cast of the spinoff. They will be joined by "Doctor Who" returning cast members Jemma Redgrave as Kate Lethbridge-Stewart and Alexander Devrient as Colonel Ibrahim.

"The War Between the Land and the Sea" takes place in a world where a fearsome ancient species emerges from the ocean, presenting itself dramatically to humanity and triggering an international crisis. With the entire population at risk, UNIT, the Unified Intelligence Taskforce, steps into action as a war erupts between the land and the sea.

The spinoff was created by "Doctor Who" showrunner and executive producer Russell T Davies, who also co-wrote it with Pete McTighe, known for his work on "A Discovery of Witches," "The Pact," and "Doctor Who." The series marks the return of the Sea Devils, classic "Doctor Who" villains who were first introduced in 1972.

Expressing his excitement about the project, Davies stated, "I'm so lucky to work with such a magnificent cast. And this is a huge, muscular, thrilling drama which will shake The Whoniverse to its foundations. When the Doctor's not in town, the whole of humanity is in trouble."

Both Russell Tovey and Gugu Mbatha-Raw have previous connections to the "Doctor Who" universe. Tovey appeared in the series over a decade ago as Alonso Frame, while Mbatha-Raw portrayed Martha Jones' sister Tish in four episodes. In the spinoff, however, they will be taking on new roles.

Filming for "The War Between the Land and the Sea," produced by Bad Wolf with BBC Studios for Disney Branded Television and BBC, is set to commence next month. The series will be exclusive to Disney+ where available and will also air on BBC One and BBC iPlayer in the U.K.

In addition to Russell T Davies, the executive producers of the spinoff include Phil Collinson, Joel Collins, Julie Gardner, and Jane Tranter. Dylan Holmes-Williams, director of two "Doctor Who" season one episodes, will helm the new series as its director.

During the panel, other exciting announcements were made regarding "Doctor Who." Nicola Coughlan, known for her role in "Bridgerton," revealed in a special video message that she would star in this year's Christmas special as Joy, a character whose life is forever changed upon meeting the Doctor. Ncuti Gatwa and Millie Gibson, who portray companions to the Doctor, will be returning for the upcoming season. They will be joined by Varada Sethu and Jonah Hauer-King, who will take on new roles in the show.

The most recent season of "Doctor Who" brought about a new era with Ncuti Gatwa stepping into the role of the 15th Doctor. Gatwa's casting marked a significant milestone, as he became the first openly queer Black actor to portray the iconic character. Gatwa expressed his enthusiasm for the diverse casting, highlighting the essence of the show's concept of regeneration.

Fans of "Doctor Who" also had the opportunity to immerse themselves in the beloved series at the convention's show floor, where a themed photo-op inside the TARDIS was set up. Additionally, on International Friendship Day, showrunner Russell T Davies will participate in a creator-to-creator conversation with "Star Trek" showrunner Alex Kurtzman, discussing storytelling across time and space.

With the announcement of "The War Between the Land and the Sea" and the exciting developments for the upcoming season, "Doctor Who" continues to captivate audiences with its imaginative universe and diverse casting choices. Stay tuned for more updates on this eagerly anticipated expansion of the Whoniverse.