A Klingon Great House with a seat on the High Council, renowned for spies and deception rather than open battle, and the house of L'Rell's mother and of her uncle Ujilli.
The House of Mo'Kai is one of the Great Houses that answer T'Kuvma's beacon in the Discovery episode Battle at the Binary Stars, where it is represented by Ujilli. The house specialises in spying and subterfuge, skills other houses regard as dishonourable.
L'Rell, born to a Mo'Kai mother and a father of T'Kuvma's house, draws on those arts throughout the first season, most drastically in the surgery that turns Voq into the human Ash Tyler. In Lethe the house helps set a trap for a Federation envoy on Kol's behalf, in which Admiral Cornwell is captured, and is rewarded with cloaking technology.
After L'Rell becomes chancellor the house backs her, and Ujilli is murdered by Kol-Sha's followers in Point of Light. The name first appeared in Voyager's The Killing Game, in which Janeway, cast as a Klingon in a Hirogen holoprogram, fights for the House of Mo'Kai.