The Alvis program was instigated by the Japanese government after the Seto Inland Sea Mir rendered everyone in Japan infertile. Each Alvis (Tatsumiyajima, Horaijima and Watatsumijima) took a portion of the Mir with them, but the Mir fragments on Alvis-2 and Alvis-3 (Horaijima and Watatsumijima, respectively) were lost. Horaijima's became the Master-type Festum Idun and Watatsumijima's was removed by the Neo U.N. to form the core of the Azazel-type Festum Vagrant. This means that as of 2150, Tatsumiyajima is the only Alvis operating in its original capacity, though Watatsumijima's core was replaced by Ashoka. Horaijima, meanwhile, cannot be restored to a habitable capacity due to the detonation of it's core's Fenrir in 2146.
Each Alvis has also been codenamed by the Neo U.N., with Alvis-1 as D-Island, Alvis-2 as Avalon and Alvis-3 as Atlantis.