Sefenein, one of the greatest drow fighters ever, wielded this blade through his career. It is unknown wether his skill depended on the blade, or if the blade somehow absorbed his skill. He lived alone in a remote area of the Underdark, fighting the monsters until dying from old age. Whath happened to the sword after that, is unknown.
 

ABILITIES
Gives a +5 to hit and damage. It will also treat allenemies with an armor class lower than 0, as 0. Those with ac of 1 or more, are not affected by this. It will also for some reason do 1.5 times the rolled damage to all monsters of the underdark (Hook Horrors, Beholders, Illithid, etc.)

The blade grants the user immunity to the faerie fire spell, and it reduces all damage suffered by 1 point.

 If wielded by any kind of elf except a drow, it acts as a normal long sword without any bonuses/abilities.