The “Halo” series at Showtime is rounding out its main cast.

The premium cabler announced Friday that Natascha McElhone, Bokeem Woodbine, Shabana Azmi, Bentley Kalu, Natasha Culzac, and Kate Kennedy have all joined the series adaptation of the megahit video game. They join previously announced series lead Pablo Schreiber, who will play the Master Chief, and Yerin Ha, who is playing a new character named Kwan Ha.

McElhone will star as two characters: Dr. Catherine Halsey, the creator of the Spartan supersoldiers, and Cortana, the most advanced AI in human history, and potentially the key to the survival of the human race.

In addition her role in the Showtime series “Californication,” McElhone has appeared on shows such as “The First” and “Designated Survivor” in addition to films like “The Truman Show,” “Ronin,” “Solaris,” and “City of Ghosts.”

Woodbine will play Soren-066, a privateer at the fringes of human civilization whose fate will bring him into conflict with his former military masters and his old friend, the Master Chief.

Woodbine received critical acclaim for his role in the second season of the FX series “Fargo,” earning an Emmy nomination for his work on the series in 2016. He will also appear in the upcoming Hulu series “Wu-Tang: An American Saga.” His other TV credits include “Unsolved: The Murders of Tupac and the Notorious B.I.G.,” “Underground,” and “Saving Grace.” His film credits include “Strapped,” “Jason’s Lyric,” “Ray,” and “Spider-Man: Homecoming.”

Azmi will play Admiral Margaret Parangosky, the head of the Office of Naval Intelligence.

In a career spanning 40 years, Azmi has acted in more than 140 films and has won the prestigious National Award for Best Actress five times, along with every other major acting award in India. She is also known for her roles in international films like “Madame Sousatzka,” “La Nuit Bengali,” “City of Joy,” and “Son of Pink Panther.” Her TV roles include “Banglatown Banquet,” “Capital,” and “Next Of Kin,” a six-part series.

The series will also introduce three all-new characters to the “Halo” universe. Kalu will play Spartan Vannak-134, a cybernetically augmented supersoldier conscripted at childhood who serves as the defacto deputy to the Master Chief. Culzac will star in the role of Spartan Riz-028. a focused, professional and deadly, cybernetically enhanced killing machine. Kennedy stars as Spartan Kai-125, a courageous, curious, and deadly Spartan supersoldier.

Kalu’s latest film projects include “Avengers: Age of Ultron,” “Edge of Tomorrow,” “Vengeance 2,” “Stairs,” “Judy,” “Dead Ringer,” and “Black Site.” On television, he has appeared in roles including “Chimerica,” “Doctor Who,” and “Spooks.”

Culzac’s roles include the upcoming television series “The Witcher” starring Henry Cavill and “Cursed.” Other credits include “Men in Black International” and “The Strangers.”

Kennedy starred in the BBC adaptation of “A Midsummer Night’s Dream” as well as “Catastrophe” and the film “Damascene.”

“Halo” will begin production later this year in Budapest and is slated to air in the first quarter of 2021. It was announced back in June that Showtime had ordered a 10-episode series based on the megahit video game after it had been in development at the premium cabler for years, though its order has since been trimmed to nine episodes. Kyle Killen and Steve Kane will serve as co-showrunners and executive producers. Darryl Frank and Justin Falvey of Amblin Television will also executive produce along with series director Otto Bathurst and Toby Leslie for One Big Picture, Scott Pennington for Chapter Eleven, and Karen Richards.

The series is produced by Showtime in partnership with 343 Industries and Amblin Television. It will be distributed globally by CBS Studios International.

(Pictured: Natascha McElhone, left; Bokeem Woodbine, right)