Thag is the leader of the Bower Lake bandits in Fable 2 and the first boss fight in the game.
When the Hero of Bowerstone obtains the powers of a Hero, he or she heads to Bowerstone to see Theresa. However, Thag's men have terrorized the area around Bower Lake forcing the guards to close off the roads.
The Hero heads to Thag's camp who has some civilians captured in an effort to sell into slavery. Thag's men or no match for the Hero's strength, skill, and will so Thag himself faces off against the Hero, but not before kicking the Hero's dog.
Like his men, Thag is easily killed in battle and his head is made into a trophy. His death also allows the Hero to buy his cabin and the road to Bowerstone opens. The Hero is also given the option to free the captive civilians for good points or sell them him/herself for gold and evil points.