The Old Prince had restricted access to Vault so tightly that no one had suspicions of it. The adamantine and other mysterious ores the Prince smuggled into Crux were thought to be just another part of the greater mysteries that surrounded him. His successor has taken no interest in Vault. He gave up most claims to it, save for the massive Castle on Vault that over looks the Secret Sound. The new Tinkerer has announced plans to construct a bridge linking Vault to the mainland of Crux. Once completed, Crux will no longer connect just two continents, but three.
Vault is unique.
The mechanism that causes it to float is unknown. Some speculate it could be the result of some ancient artifact the Old Prince had hidden. Others surmise a mineral or substance within Vault causes the floating effect.
The fauna and flora of Vault differ greatly from Necruxa and Ainesia as well. The megafauna of Vault seem related to animals found throughout the rest of the world, but are bigger, or are vastly different in how they appear. More that are discovered remain unique and different from those found elsewhere. The megafauna are matched by the Vault Giants, an introspective folk who seem to find other intelligent folk intimidating, despite any size advantage they might have.
Ruins from the Aetheric Empire are scattered throughout Vault. Metallic, giant structures that vibrate with energies that aren't just magic but somewhere between science and magic. They bear sigils that still need translating. The recent discovery of the First City underneath the Skullmount has drawn comparisons. Some of the ruins match writing found in the First City. It remains a great mystery, however. This attracts delvers and treasure hunters from all over the world to Crux to enter the Floating Frontier.
The Android who has taken on the title of Tinkerer has begun to construct a bridge between Crux and the lowest ledges of Vault, creating an easier means for the City of Curses to expand onto the once hidden continent.