This page contains information regarding Star Trek: Discovery, and thus may contain spoilers.
He was a member of the House of Mo'Kai. His sister married a man of the House of T'Kuvma, one of the lower Klingon houses, and gave birth to his niece L'Rell. (DIS: "The Butcher's Knife Cares Not for the Lamb's Cry", "Point of Light")
Ujilli represented the House of Mo'Kai on the Klingon High Council in 2256. When T'Kuvma rallied the twenty-four Great Houses by using the Beacon of Kahless, his vessel answered the call. While hearing T'Kuvma lay out his desire to unite the Klingon people, he was keen to hear more. (DIS: "Battle at the Binary Stars")
During the first months of the Federation-Klingon War, the House of Mo'Kai was nominally independent. In December 2256, they and the House of D'Ghor secretly arranged a meeting with Vulcan to discuss the possibility of uniting against Kol's forces. They were to meet Ambassador Sarek on Cancri IV. However, the meeting was in fact a ruse by Kol to capture a high-ranking Federation official. Because Sarek was unable to attend due to having suffered from a terrorist attack, Admiral Katrina Cornwell attended the meeting instead, and was captured by Dennas and Ujilli. (DIS: "Lethe")
When his niece L'Rell declared herself to be the new Chancellor of the Klingon High Council in 2257, Ujilli was among skeptical Great House leaders present in the Klingon High Council Chamber. (DIS: "Will You Take My Hand?"
He ultimately became one of L'Rell's main supporters and helped her hide her child with Voq from Ash Tyler. Eventually, however, Ujilli decided he could not lie to Tyler any longer and revealed the child to the former sleeper agent. Soon after, Ujilli was murdered by followers of Kol-Sha of the House of Kor who kidnapped the child in an attempt to usurp power from L'Rell. (DIS: "Point of Light")
Background information Edit
Ujilli was portrayed by Damon Runyan. His name was not mentioned in DIS: "Battle at the Binary Stars", but was shown in the episode's credits. It was first spoken on screen in DIS: "Point of Light" which also clarified his relationship to L'Rell.