The Black Elf

The Black Elf is a long standing piece of folklore that people use to terrify children and to sew the evils of bad elvish. In reality the Black Elf is an agent of pure chaos and destruction, the progenitor of the Void Elves, and a devastating historical killer that seeps in and out of the flow of Aradia's history at random-showing up to decimate swatch of peoples in moments before leaving once more.
The apparent origins of the elf start in an ancient city that nobody knows the name of apparently in the heart of Obscura. The elf was a bastard child to a princess and cast away to be killed, instead he was saved by a low caste family and raised a peasant. When he learned his birthright he was angry, but he submitted there was nothing to be done. When his family was killed for having defied the will of the royalty, having caught wind that this bastard was alive, he snapped and pleaded with all the dark powers of the Void in rage and melancholy to give him the strength to make them suffer in exponential terms of his own.
Apparently a High Demon heard his pleas and had him infected with thousands of raging spirits of wrath, greed, pride, and envy. So much so that his fury was limitless and he was changed. He destroyed the city in one night supposedly and when people came to investigate they committed suicide at the sights they saw. The city was obliterated and the legend was to die, but people would always sing it, tell it, continue its legacy for generations to come.
Throughout history there are events where an unreasonably high number of sinners and innocents are slaughtered in large numbers. One such event happened to Elmer Twicefreed during an incident after the collapse of a mysterious civilization. The Black Elf annihilated an entire slaver ship, including all the innocents captured aboard only leaving Elmer alive in the hope he would become a host such as himself.
In far more recent times he was briefly spotted killing off remaining Sanistar members, townships in the surrounding area, and assaulting Fairmane. He was later 'killed' by Divankul Dul-Sansiska. 
However, this is not where the story ends for this powerful host of wrath, he needs to come back around an finish what he's been doing.