Abyss (アビス Abisu) is a mysterious place which is rumored to be a place where people will be taken and suffer a fate worse than death. Anyone whose count reaches zero will be taken to the Abyss by mysterious black hand called Althing.
It is later revealed that the Abyss is actually a ruined Japan after the Abandonment War. There live a bunch of children who were not chosen by Althing. Due to the scarcity of natural resources, the Abyss has only a few people. The country is ruled by Sakai Tokikaze, the King of Abyss and the Blink Baron.
Unlike Althea, Abyss still retains its modern weapons and technology such as nuclear weapons and airplanes. However, due to Althea's taking a majority of resources from the surface of the planet such as fuel, these weapons are rendered useless and due to the power of the Original Ballots to vote and enforce new laws into the world, its impossible to actually use the nuclear weapons stored in the Abyss.[1][2]