Who is D'Artagnan from The Vicomte de Bragelonne and what is their importance?

D'Artagnan is one of the famous Musketeers and the only one still in service. Unlike the others, D'Artagnan has not reached his preferred status in life. Also unlike the others, he is loyal to Louis XIV. D'Artagnan dies just after reading a proclamation that he has been named a marshal of France.