This quest is not available in game.
Bring 5 Scaber Stalks and 1 Death Cap to Barithras Moonshade in Auberdine.
I am devising a potion that requires rare mushrooms, mushrooms that grow only in a certain cave. The cave lies behind Cliffspring Falls, to the east and slightly north along the mountains.
I would go there myself, but I was advised by the Grove of the Ancients to stay away from that place. Our venerable allies sense that the cave is the hiding place for a new evil in Darkshore.
Please, <name>, gather the mushrooms for me. And while doing so, scout the cave to confirm the Ancients' fears.