Sigma-One was a COG Gear squad that assisted Delta-One when they were ambushed on the way to Montevado. Sigma-One killed a Brumak that was threatening Delta-One before returning to Jacinto. Sigma-One later took part in Operation: Hollow Storm and the Assault on Landown. It is known that they made it to the Hollow; however the squad was later separated. All of its members, save for Cole and Baird, were killed by the Locust. The surviving members of the squad entered Delta-One. It was later reformed, but it is unknown who was in it.