Halo isn’t envisioned to be Showtime’s Game of Thrones. “It’s our Halo,” counters network programming chief Gary Levine.

Appearing at the Television Critics Association summer press tour on Monday, Levine and Showtime Networks president/CEO David Nevins reiterated their stance that the recently announced, live-action adaptation of the Halo videogame — the killer app for the original Xbox, as Halo: Combat Evolved — is no less than the premium cabler’s “most ambitious series ever.”

As a TV series, Halo will dramatize “an epic 26th-century conflict between humanity and an alien threat known as the Covenant,” weaving “deeply drawn personal stories with action, adventure and a richly imagined vision of the future,” the network previously said.

At TCA on Monday, Nevins further described the Halo series as “futuristic, space-based science-fiction” in the vein of Star Trek. “It’s not fantasy.”

Kyle Killen will serve as executive producer (as will Steven Spielberg), writer and showrunner, which on the surface seems like a curious fit, given his previous TV credits: Lone Star, a drama about a Texan con man leading a double life, and Awake, in which a widower toggled between two realities.

Nevins, though, said that he feels about Killen the same way that he felt about Homeland‘s Alex Gansa before that series became a hit (and is now entering Season 8). “His moment is coming,” the exec avowed.

Plus, Showtime made “a conscious decision” to enlist for Halo writers “not known for sci-fi, not known for big-battle movies,” so as to “get under the armor of the Spartans” aka the supersoldier space Marine characters.

Meaning, yes, franchise front man Master Chief will be a character on the series, Nevins affirmed.

Update: THR on Nov. 1 reported that the roles of “Dr. Halsey” and “Jenny” (an Asian woman age 18 to 20) are also being cast.

On track to premiere in 2020, Halo is not in production yet, though Showtime brass have seen scripts, Nevins said. And at first blush, he believes the ambitious series “will have enormous appeal to Halo fans and also appeal to the Showtime drama fans.”