Monkey D. Dragon is the father of Luffy and the son of Monkey D. Garp. He is the infamous Revolutionary Leader and has been causing trouble around the world.
His personality is mostly unknown due to the many mysteries surrounding him, save for an apparent love for freedom and belief in fate, which are traits of aD . Unlike other members of his family, or D's for that matter, he looks stern and serious, though in all his appearances so far, he wears a smug grin. He speaks as though he is a mystic of sorts.
Dragon is most wanted by the World Government. According to the World Government, he has some very dangerous ideals. The World Government has trouble capturing him, not to mention his tremendous bounty which is unknown at this time (He holds the title of "The World's Most Wanted Man").
Dragon's history remains mostly a mystery, thus it is unclear why Luffy was left to be brought up by his father Garp instead of himself. At some point he began the Revolutionary movement becoming its leader and his ideals began to slowly spread throughout the world. One by one countries slowly began to support him, though sometimes through war.
The little known history on him is that Six years ago, the Council of the Kings in Mariejois. The meeting was to discuss his revolutionary movement and his ideals that were threating the World Government. Thalassa Lucas showed the picture of him.
His first appearance was during the Loguetown Arc where he saved his son Monkey D. Luffy from Captain Smoker. He stopped Smoker from killing his son. He then warned Smoker not to interfere with Luffy's ambitions. At that moment a gust of wind passed through LogueTown blowing Luffy, Smoker andBuggy the Clown away. It's not known if he controlled the wind that blows off the marines at this point, but in the manga he did say the word "Storm" as the wind passed by and seemed untouched by it.
While visiting Luffy, Garp let slip that Dragon was Luffy's father in a causal conversation with him. The reaction of those present was of dire shock. It was then revealed to Luffy just who his father was by Robin.Robin stated that he was the top of the revolutionary army and has spread his ideals to every nation and kingdom, causing many of them to fall into his hands. He manages to stir rebellion around the world and has successfully pushed the world towards civil war. His actions greatly anger theWorld Government and he is considered the most dangerous man in the world. Until that moment, no one had known anything about Dragon, not even his full name.
He has since reappeared again on Paladego. Seeing Luffy's new bounty one of his men was about to tell him that Luffy was Vice Admirals Garps grandson when Dragon stops him and says he will stay in the wind for a while. He walks out into the castle's balcony where he remarked that the true nature of the world will be answered and he will meet Luffy again