'It is Earth-year 2391. Through a vast tear in the fabric of the universe, alien warriors emerge to fight an already embattled humanity. The sky is burning. The Gateless Gate has opened. The cosmic rip meanders like a burning string across the galaxy and slices through the asteroid field near the orbit of Jupiter. The great opening becomes known as, "The Mumon Rift"...'
This setting was first created for the WARS Trading Card Game, and was later adapted and expanded by Moongoose Publishing's "WARS Roleplaying Game".