At long last, Showtime's upcoming adaptation of Halo is coming into focus. The project has been in the works for a very long time, but since the news broke that American Gods alum Pablo Schreiber will portray the iconic role of Master Chief John-117, not much has been revealed. That all changed at Showtime's TCA press tour presentation, though, with several major casting announcements.

The biggest is the addition of former Californication star Natasha McElhone, who will play two roles on the series. First, the actress will play Dr. Catherine Halsey, the person behind the Spartan supersoldier program that created Master Chief. Taking a page from the games, she will also play the artificial intelligence construct Cortana, which is based on a cloned copy of Halsey's brain. Showtime describes Cortana as "the most advanced AI in human history, and potentially the key to the survival of the human race."

Beyond Cortana, five additional castings have been announced. Bokeem Woodbine (Overlord) will play Soren-066, a character who first appeared in the short story Paria from the Halo: Evolutions--Essential Tales of the Halo Universe collection. Showtime describes Soren-066 as "a morally complex 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."

Shabana Azmi has taken on the role of Admiral Margaret Parangosky, a character mentioned throughout multiple iterations of Halo. The character, who made her first appearance in the Halo: Ghosts of Onyx novel, is in charge of the Office of Naval Intelligence. While Showtime says little else about the character, in Halo lore she has a not-so-friendly history with Halsey.

The rest of the new roles are for characters created for the series--all Spartan soldiers. Bentley Kalu (Avengers: Age of Ultron) plays Vannak-134. This cybernetically augmented troop is essentially Master Chief's deputy in the USNC, which he was conscripted into as a child. Natasha Culzac (The Witcher) is taking on the art of Riz-028, "a focused, professional and deadly, cybernetically enhanced killing machine." Lastly, Kate Kennedy (Catastrophe) plays "an all-new courageous, curious, and deadly Spartan supersoldier" in Kai-125.

It was previously announced that Halo would also see newcomer Yerin Ha play Kwan Ha, "a shrewd, audacious 16-year-old from the Outer Colonies who meets Master Chief at a fateful time for them both." Halo is currently scheduled to debut on Showtime in the first quarter of 2021, with filming set to begin later this year in Budapest.

Disclosure: Showtime is owned by CBS, the parent company of GameSpot.