The archipelago of Caelum Insula floats over the great waves of the Azure Expanse, drifting through the clouds between Chandaria and Enulon. The islands themselves are as old as Argena itself, and have deep connections to the Gods.
Caelum Insula is also called the Cradle of Life because it's thought to have been where the Gods experimented when creating life. The few that have been to the islands claim to have seen bizarre monsters and aberrations.
The reason so few people have been to Caelum Insula is because it's impossible to determine where the archipelago will be at a given time over the millions of miles of ocean between Chandaria and Enulon. Most of the travel to Caelum Insula these days is via teleportation routes that were established long ago.
Caelum Insula also holds historical significance as the place where the Scourge began. During the Great Dissension, Caelum Insula was a highly contested area because of its undetectability. Whichever side controlled Caelum Insula had an unlocatable base of operations on the Material Plane.
The Gods of the Lower Planes claimed the islands for themselves at the beginning of the Great Dissension and held it for the majority of the war. They used it as a staging grounds for their forces on the Material Plane. Once the forces of the Upper Planes realized that the Lower Deities were staging from the islands, they began searching. They searched for years without finding anything. As Anteitic ideologies grew stronger and reached a tipping point, Kadarin, an Ancient Archmage in the service of the Lower Deities assisted the Archmages of the Upper Deities in locating the Islands. With that, the Upper Deities planned their assault.
As the battle got underway and the two sides clashed in combat, the mages of both sides suddenly turned, firing upon both sides' armies. With the element of surprise, the Anteity League easily forced both sides to retreat, claiming Caelum Insula for themselves. This event is known as the Divine Betrayal, and marks the beginning of the Scourge.