Plague demon

Plague demons were fiends that were created when creatures succumbed to the abyssal plague.

Creation
Similar to ghoul fever, a victim infected by the abyssal plague, either through the ingestion of or contact with voidharrow, exposure to the blood of another infected creature, or the attacks/death throes of a plague demon, could develop symptoms of the disease and transform upon their death.

Should the infection take root, the victim began to grow dark-red crystalline sores appearing to be laced with silver and containing flecks of gold. These sores spread across the body, causing the victim to become even more contagious, but they also became more resilient and willful. Eventually, the victim would die and their corpse would explode, creating a fully formed plague demon.

Sometimes an infected creature would die before the infection of their body was complete. These creatures would still rise as plague demons, but they would be lesser, undead corpses.

Ecology
Plague demons were under the control of the voidharrow, the sentient Abyss located in another universe. The voidharrow desired to spread the abyssal plague across all known worlds, including Toril.

There were five known types of plague demon:
 * Animated corpses: Formed from a creature infected by the abyssal plague who died from a cause other than the disease itself.
 * Abyssal plague demons: The most frequently documented carriers of the plague, usually roughly humanoid in appearance in accordance with the disease's most common victims.
 * Abyssal plague swarms: Hive minds of tiny demonic insects spawned from orbs found near areas experiencing the plague.
 * Swarmbringers: Resembling spiders, swarmbringers were more intelligent and could infect the ground around them if they were killed.
 * Voidharrow doomcallers: Capable of infecting entire countries by itself, doomcallers communicated directly with the voidharrow and could launch plague-filled spores into the air.

History
In 1479 DR, plague demons were encountered in Akanûl, Luskan, and Easting.