The trailer for The Walking Dead: The Ones Who Live reveals a yellow gas that connects to two other shows in AMC's zombie franchise. The gas, previously explored in The Walking Dead: World Beyond, is a weapon developed by the Civic Republic Military (CRM) to slow down zombification. In World Beyond, the gas was used to wipe out settlements and survivors. 

The gas seen in The Ones Who Live is likely an upgraded version of the same chemical. The connection between the shows suggests that the captives taken by the CRM, including characters like Heath from The Walking Dead, were used as test subjects for the gas.

 The trailer hints at a team-up between the main characters of The Ones Who Live and World Beyond, as they work to stop the zombie virus and thwart the CRM. The gas is a significant plot point that ties these shows together in the larger Walking Dead universe. The Ones Who Live premieres on AMC on February 25.