During the Triad War, when the dwarf and elf kingdoms fought the dragon imperial forces and each other for supremacy of Duir’Aion, the dragon overlords realized they had a problem. The dwarves and elves were too many in number. Worse the sun god Aeruus had bestowed them both the power of the paladin as well as the secret of dragonslaying. Their empire was in jeopardy. So the wisest among them decided that only a truce would end the war. And the only way a truce would be acceptable was if each faction made a great sacrifice.
The dragons drafted the Martyr Compact. It proposed that each faction would sacrifice an entire clan to the Pit. The sacrifice would weaken each faction so that further bloodshed would be foolish. It would also be meaningful enough that each faction would feel that continuing a war after such a sacrifice would be dishonorable.
It took some time, but the elves and dwarves reluctantly agreed (the dwarves were particularly stubborn about it. The elves knew the numbers sacrificed would have been more than tripled if the war continued. The dwarves were concerned about the hole created in their connected underground kingdoms.
So all the Princes all eight elven kingdoms, one for each subrace of elves, gathered under the night of the full moons. Each drew lots, a strand of unicorn hair. At the end, the Prince of the shadow elves, and by extension the shadow elves themselves, held the shortest strand.
A ritual began a month later with the shadow elves, joining the dwarf and dragon sacrifices, on the summit of Dragonspine Mountain. Dwarves, elves, and dragons gathered to perform the ritual. On its completion all three clans vanished. The Compact satisfied, the three factions left to mourn their losses, and to celebrate, soberly, the end of the war.
Elven sages believed the shadow elves were destroyed. Magical attempts to locate and communicate with them failed after a few days. No mortal had ever lived in the Pit, home of demons and devils alike. While they were partially right, they couldn’t have been more wrong.
The shadow elves in an effort to save themselves from destruction agreed to servitude to a devil Prince. The devil shattered their souls and collected the fragments. What nefarious purpose is unknown, but rumor has it the Prince was attempting to elevate himself to a King, a rare title among infernals. In return for their souls and servitude, the Prince taught them infernal magic. The soulless elves found themselves drawn to rune magic, a primal and ancient magical tradition.
The shadow elves eventually overthrew their captor, and split the collected souls among their number. There was only enough to give each a fragment of a soul. This also enhanced their connection to runic magic, bestowing each of them a rune of power. Calling themselves rune elves, they established themselves as mercenaries to the infernal lords. Eventually, they were able to parley for a portal back to Duir’Aion.
The rune that gives the daemon elves, as they are also known, their power is a bit of potent infernal magic. At it’s basic, it allows a rune elf to draw a bit of spark, the divine energy in a soul, into themselves. Absorbing the spark enhances the rune elf. Absorbing more allows the elf to absorb more of their foe, absorbing talents, racial abilities, even class abilities. An rune elf possessing a greater rune can even become a copy of those they absorb.
Centuries had passed since the elves saw their home. No matter. The rune elves have only goal in mind. The utter destruction of the elven realms. Their time in the Pit have twisted them into creatures of great evil. Each one believes with the death of each elf (not rune elf) they will earn a piece of their soul back. Earn enough and they will metamorphosize into a shadow elf.
It should be noted that while the typical rune elf displays the soul rune, other runes are known to exist. The archmage daemonlord sports an arcane rune, enhancing his already potent arcane might. Death runes, demon runes, even dragon runes are known to exist.
A Darkness Rising 