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.

History
Long ago, the flying city-state of Aeor was a place of invention and magic. Held aloft by brumstone, 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.

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.

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.