Qabalrin

The Qabalrin are a now extinct group of elves that existed on Eberron at the same time as the giants of Xen'drik, and were destroyed before the giant's war with the Quori and the downfall of the giants.
The Qabalrin elves occupied a city state southeast of where Stormreach is located today. They were the first mortals to discover the secrets of necromancy, and they are believed to have been the source of the first vampires. The existence of this city state is hotly debated by scholars, the idea of an elven civilisation that the giants feared seems ludicrous, especially given evidence of the elves enslavement to the giants.
According to recovered records from the Cul'sir Dominion in Xen'drik, the giants were taught arcane magic by the god Ouralon, who cast a gigantic shadow over an island of elves. These elves embraced Ouralon's shadow, and it taught them the secrets to dark magic. These elves practiced magics that were forbidden by Ouralon and broke the laws of life and death. The giants feared the magic of these elves, but even they lacked the might to do anything about them. The records state that Ouralon himself decided that the Qabalrin had to be stopped. Supposedly, Ouralon ripped the heart of Siberys from the dragon's corpse and hurled it at the city of the Qabalrin elves, utterly annihilating them. The impact was said to be so powerful that it formed the modern day Ring of Storms.
Regardless of the truth of those records, a few concrete facts remain. There was an independent city state of elves that existed independent of those that were enslaved by the giants, and that civilisation was destroyed when a cataclysmic Siberys shard fell from the Ring of Siberys. Those that survived were refugees who joined up with the other elves on Xen'drik, and eventually joined Aeren's exodus to the land that would become Aerenel.
Those refugees were not the greatest of their people, but even so they had an advanced knowledge of necromancy that was unheard of at the time. These scattered Qabalrin elves would become the elven faction known as the Line of Vol.