World of Warcraft Quests involving Mosshide Mongrel:
The Ranger Lord's Behest Travel to the northern borders of the Eastern Plaguelands and recover the Quel'Thalas Registry. The item is somewhere in the Quel'Lithien lodge.
You must also slay 8 Rangers, 8 Pathstriders, and 8 Woodsmen.
Stonetalon Mountains Alliance Quest
A Gnome's Respite Kill 10 Venture Co. Loggers, and 10 Venture Co. Deforesters and return to Gaxim Rustfizzle in Stonetalon.
Wetlands Alliance Quest
Tramping Paws - (Step 1) Kill 15 Mosshide Gnolls and 10 Mosshide Mongrels, then return to Rethiel the Greenwarden in the Wetlands.
Eastern Plaguelands Alliance & Horde
When Smokey Sings, I Get Violent Travel to Plaguewood, northwest of Light's Hope. Destroy 8 Scourge Structures by using Smokey's Special Compound at the Mark of Detonation planted inside each building. Smokey has had the Ziggurats and Slaughterhouses marked.
Once you plant the bomb, leave the building and marvel at your handiwork.
By the way, Smokey's Special Compound is rather... unstable.