Bring 5 Vials of Innocent Blood to Apothecary Lydon in Tarren Mill.
I will create a toxin to bleed the violence from the Venture Company, rendering them weak and docile. That should fix the Horde's problem in Stonetalon, yes?
But to create the toxin, I will need the blood of innocents, a difficult ingredient to obtain.
Fortunately the Syndicate, a group of human brigands in this area, employ shadow mages... and those mages collect innocent blood for their own, unsavory purposes.
You can find the Syndicate shadow mages in Durnholde Keep to the southeast.