Who is Don Blas Vivar from Sharpe's Rifles: Richard Sharpe and the French Invasion of Galicia, January 1809 and what is their importance?

Don Blas Vivar comes from a noble aristocratic Spanish family. He feels most at home, however, with his rural troops.... the Cazadores. Vivar has an easy way with his men, and he inspires their respect and admiration. He is best known for his ability to deceive, and he deceives everyone.