Phantom Hive

the space between the Hill and the Underworld, made up of drifting archipelagos of magical land floating in the Intraplanar Void. In its center is a towering fortress where most Phantoms live.

Phantoms are a race of Undead born when an attempt to create another kind of Undead goes wrong or, in rare cases, when someone is infected with Phantom Essence. Phantoms remember very little of their previous lives in most cases, and their powers manifest as representations of their former soul's worst fears.

Phantom Essence is a sort of ectoplasmic substance that Phantom Magic is made of- taking the form of either smoke or oil, it hangs in the air and runs through the rivers of the Hive. It is incredibly corrosive, and prolonged, deliberate exposure to it can lead to the person exposed being painfully morphed into a Phantom.