Thorned Warriors are Natarian troops. These are the equivalent of Gallic swordsmen, i.e. primary attack unit, with further lowered defensive capability. Thorned Warriors, like all Natarian units, are controlled by NPCs , and players can not train or fight with them. For travian advice go here
"The thorn-like extensions on their helmets, bracers and shoulder-parts of their armour give the Thorned Warriors their name. The men who fight for the Natars as Thorned Warriors are persistent and well trained, offering a bloody battle to anyone who is foolish enough to attack them."
These troops are part of the forces that protect Natar villages, and attack World Wonder villages.