Halo: Nightfall: ONI: Unit 54

ONI: Unit 54 is a Second Story of Halo: Nightfall's Episode 2: Sourced From Hell. The featurette depicts a transmission between Ader Haddak of Sedran Emergency Response Unit 54 and ONI scientist Noah Caloes, regarding the bioweapon dispersal method used in the terrorist attack in Sedra City on February 7, 2556.