Aeor

 was a pre-Calamity floating city that crashed in Eiselcross, currently being excavated by a few outposts for the ancient relics to be found there.

A5
At the A5 crash site is a room in which was embedded a particularly large (one-and-a-half to two feet wide) threshold crest, which are used for teleporting entire cities even between planes.

Cognouza Ward
One section of the city of Aeor was called the Cognouza Ward, and the leaders of that ward were called the Somnovem. The Somnovem orchestrated Cognouza's escape from the destruction of Aeor, and wish now to return. They betrayed Aeor to ensure their survival.

History
Long ago, the massive flying city-state of Aeor was a place of invention and magic, ruled by its mages, and considered one of the most powerful of the pre-Calamity arcane societies. Held aloft by brumestone, the bluish stone used in sky ships with the property of being easily enchanted to lift, Aeor's people had grown powerful enough to create weapons capable of killing the gods. During the Calamity, a consortium of both the Prime Deities and Betrayer Gods called a truce long enough to crash the city onto the island of Foren in Eiselcross. It is believed that there were no survivors from the fall of Aeor.

Aeor was long believed to have been obliterated and its location forgotten. Recently, however, artifacts and relics have been discovered, and Dwendalian, Uthodurnian, Xhorhasian, and mercenary expeditions search the hazardous terrain of its crash site for more. There are some Empire outposts there that are currently excavating what remnants they're able to have access to of the fallen city, including the central outpost of Balenpost.

According to Babenon Dosal, artifacts from Aeor started making their way down into the Empire around 828 or 829 PD.

Caleb was able to recognize and recall that the material used to power both the golems and the collar that he recovered from the Heirloom Sphere does not exist naturally, but was utilized as an arcane battery-type technology that was employed by some of the top echelon of archmages during the Age of Arcanum, and that some elements of it had been traded, usually scavenged from the ruins of Aeor to the north.

Lady Vess DeRogna offered the Mighty Nein unspecified work "in the north" to be done sometime after the peace talks concluded. When the party inquired at her residence, she asked for their assistance with an expedition to Foren to investigate Aeorian ruins for artifacts.

Fauna

 * Aeorian hunters
 * Aeorian absorber
 * Aeorian nullifier
 * Aeorian reverser