Phyrians

A nightmarish species of legendary horror, widely considered Demons by most species with the notable exception of the Elves who worship them as servants of the Angel of Death.  The Phyrians have not been seen in the Middle Realm for 800 years.

According to Elvish mythology, the Phyrians came from the underworld, summoned by a powerful spell found in death's spell book, they were accidentally unleashed by a the dark magician Grale who tried and failed to control the magic of death.  The Phyrians were unleashed upon the world in an event known as the Phyrian wars.

 Phyrians are large, jellyfish like beings with tentacles and large bat like wings.  They lack skeletal structure and are partially buoyant, giving them great speed in the air.  They have massive clawed hands and black, expressionless eyes, they do not speak and are thought to communicate psychically with each other.

Phyrians are highly intelligent and magic beings, being underworld lords they have necromancy and death magic more powerful than any in the middle realm, even the Fairy King.  Killing all in their path and leaving the land a barren waste, they conquered all in their path and raised a great army of undead zombies, skeletons and unspeakable twisted abominations. 

Putting aside their long standing hatred, the Elves, Humans, Smithkin, Gnomes, Dracilians and Fae all fought a multi front war against the Phryians, all suffering massive losses but ultimately slaying and driving back the Phyrians into the Underworld and sealing the portal with portal with high magic.  The aftermath of the Phyrian war lead to the Second Dark Age and ultimately lay the ground  for the Alliance of Humans, Elves, Dracilians, Smithkin and Gnomes.