Rise of the Twilight Empire
Gnolls are a product of the demon lord Yeenoghu. They are exceptionally cruel and sadistic, even by beastman standards. About 150 years ago, an army of gnolls sacked the White City, capital of the Empire of Nerath, desecrating its temples and slaughtering its people. Now the city is nothing but a demon haunted ruin, and the great gnoll horde dispersed across the countryside. A substantial number have made their way to the Nentir Vale, plaguing travelers along the roads and anyone who ventures too far into the forests.