You have no doubt seen the worgs which the Blackrock orcs command.
It is curious - no matter how many we destroy, their numbers never dwindle. My scouts have reported that the worgs are bred, trained, and ultimately exported from Blackrock Spire: capital city of the Blackrock orcs. You must travel to Blackrock Spire and discover the source of this menace. Discover... and destroy.
Good luck, <name>. May Cenarius protect you...
Do not dwell upon her suffering, <name>. The beast was corrupt - a product of dark magic. You have done the Alliance a great service and you shall be rewarded.