Originally Angor was a extra dimensional planet, protected by the Champions of Angor (also known as the Assemblers and the Justifiers). They clashed with the Justice League of America when this world was invaded by the robots of Cam-Nam-Lao. The league and the Champions faced each other in Cam-Nam-Lao where both leave in friendly terms after a brief skirmish.
After the Crisis on Infinite earths, it would be revealed than Angor, now inside of the main universe, was destroyed by a nuclear conflict and only a handful of superbeigns survived. This would later be expanded to reveal other more dangerous survivors: the Extremists, supervillians who destroyed their own planet, leaving only automatons from a theme park as the last remains of their civilization.
After the Infinte Crisis, Angor became defacto the alternate earth of the dimension of Earth-8. The Justifiers became the Meta-Militia.
After Flashpoint, the new earth 8 was called Angor again in the 2017 Justice League of America series, being basically the native equivalent to "Earth", meanwhile the defenders of the world were rebranded as the Retaliators.