Mar'nah at Sun's Reach Harbor wants you to travel to Razorthorn Rise in Outlands, collect 5 Razorthorn Roots, and return to her.
My stocks are presently sufficient, but I'll need plenty of razorthorn roots to keep up with the demand.
Collecting the roots is difficult, but I know a special method of extraction.
Using the glands of the Razorthorn flayers, one can control a ravager there and use it to expose a root.
To find the roots, travel to Outlands and fly northeast from Shattrath until you reach Razorthorn Rise.
Return to me, [player], once you have collected five of the roots.