This quest is not available in game.
Speak with Mathias Shaw in Old Town Stormwind. He resides in the Barracks.
Nathanos Marris was the first and last of the human ranger lords. A disciple of Sylvanas Windrunner, now the Banshee Queen of the Forsaken.
We had thought that Nathanos had been killed in action in the defense of Lordaeron five years ago. Although his corpse was never recovered, it was assumed that he did not make it out of the Eastern Plaguelands.
Mathias Shaw has been investigating the disappearance and may have some new information. Report to him at once. He resides in Old Town, at the Barracks.