Well, this is weird. Laura Shigihara, the voice of Plants vs. Zombies' Sunflower, and the songwriter behind the game's theme tune, decided to cover one of Warcraft's most famous songs. And it's pretty great!
The Lament of the Highborne is heard in World of Warcraft when Blood Elf players finish the quest The Lady's Necklace, which requires them to return a locket to Sylvanas Windrunner, a former High Elf who is now the leader of the undead forsaken. A gift from her long lost sister Alleria, the locket moves the typically moody Dark Lady to summon a choir of Banshees and sing the funereal dirge to the player, in remembrance of the fall of the High Elf kingdom of Quel'thalas.
So it's a little weird to hear it from the voice behind this thing: