Ancestral Guardian

Ancestral Guardians are human ghosts that roam the Chamber of the Moon in Uldum. Many are engaged in battle with the Schnottz Elite Troopers that have invaded the chamber.

In Hearthstone
The Ancestral Guardian appears as HS Ancestral Guardian (a common card) for the paladin class in the Saviors of Uldum expansion for Hearthstone. The flavor text reads: "No one knows whose ancestor he is, but he's still upset that you never call."

A named Ancestral Guardian known as HS Kham appears as one of the bosses that can be encountered in the HS Tombs of Terror adventure.

Speculation
The Ancestral Guardians may originally be from the Wastewander bandits, though those are by no means ancestral. These humans may indicate that there were vrykul in Uldum from whom they descend after the curse of flesh affected them like with the vrykul in Northrend. Or it could simply be a joke.