The Unified Atheist League are first seen when Cartman wakes up in the future. They tell him that something happened in his time which made the world Atheist, creating the group. Before they could go into more detail, they are attacked by the United Atheist Alliance, who they reveal they are at war with.
In the next episode, "Go God Go XII", they attack the United Atheist Alliance's capital while the UAA are attacking the Allied Atheist Alliance (AAA). Cartman uses the Crank Prank Time Phone to cause Ms. Garrison and Richard Dawkins to split, consequently stopping the world from turning Atheist and ending the war. The UAL, now together with the AAA and the UAA, send Cartman back to the past.
The UAL have pointed hats that look like dildos.