The Inhumans, a race of superpowered characters led by their king Black Bolt and queen Medusa, were initially meant to get their own movie in 2018. That film was removed from Marvel's calendar this year, but Agents of S.H.I.E.L.D. had already introduced the concept of Inhumans to the Marvel Cinematic Universe, albeit without using any of the main characters.
At this point, many fans assumed that the Inhumans would be restricted to the world of Agents of S.H.I.E.L.D., but it looks like Marvel hadn't given up yet. A new series titled The Inhumans will debut in fall 2017, with the first two episodes released worldwide at IMAX in September—a first for any live-action TV show.
Marvel announced the news with a strangely businesslike post on its website, emphasizing the corporate partnership between ABC Studios and IMAX, but shared little information about the show's creative side. Our only hint is that The Inhumans "will explore the never-before-told epic adventure of Black Bolt and the royal family," with no showrunner or casting details revealed. It's unclear to what extent it will link to the Inhuman worldbuilding of Agents of S.H.I.E.L.D., if at all.