Shadesoul Curse (concept)
The Shadesoul Curse is an arcane disease that transforms its victim into an immortal, malignant Void-aligned being commonly known as a Blackspawn. Though it manifests in a whole sleuth of symptoms over time, the earliest and most universal one is an affliction with dreams that the Blackspawn feels an almost irresistible urge to enact in the waking world — dreams that are almost invariably destructive in nature.
The curse is the result of a shade possession that, for reasons unknown, does not kill the victim but seemingly fuses with or replaces their soul; children seemingly being much more susceptible to this. Very rare in most of Aeras, its highest concentration of bearers is in the ranks of the Redland cults, where it is intentionally given to newly-recruited initiates.