The Shadow Army is a malevolent ancient empire ruled by the Shadow Lord from the Shadowlands, and one of the many villains of Deltora Quest. Fallow and Thaegan are part of this army because of their alligence to the Shadow Lord himself.
Most of the monsters and soldiers which this army is made up of, the Shadow Lord had created in his Factory.
In the past, he used this army in his attempt to conquer the land of Deltora, which Adin stopped, when he defeated him in the famous Battle of Deltora.
The Shadow Lord reestablish his Shadow Army once again to began his conquest of Deltora while hunting down the descendants of King Adin of Del centuries later. His entire wicked empire was later defeated and overthrown by many Deltoran natives united by Lief, Barda and Jasmine, 3 friends who together gathered the Belt of Deltora and its seven gems, used their power with the aid and faith of the 7 tribes of Deltora to destroy the Shadow Lord and the Shadow Army once and for all.