Deathstalker

The Deathstalkers, also called Darkstalkers, are the assassins' guild of the Forsaken and the elite guard of the dreadlord Varimathras, the majordomo of the Banshee Queen Sylvanas Windrunner. The Deathstalkers also function as the Forsaken's equivalent of the Shattered Hand, a rogues' guild and spy network, reporting their information directly to their dread master.

Deathstalkers are highly trained and extremely dangerous. They are rightfully feared as the best assassins in the world not only for their skills, but because they are undead. Deathstalkers have no need to eat, drink, sleep, rest, or even breathe air. They never feel physically tired and possess tremendous willpower. Deathstalkers can remain submerged in water indefinitely without any need to rise, and can wait as long as it takes for their target to arrive. They can even pose as corpses, since by all means, that is exactly what they are.

Speculations
Some fan speculate that Deathstalkers were originally the members of the Bandit Army led by Blackthorn raised as undead by Sylvanas.

Aleric Hawkins may be the new leader of the Deathstalkers due to his blatant insistence that he is not. After all, it is not the best of positions to have after the Battle for the Undercity.