Ramsay is the bastard son of Roose Bolton, best known for the sadistic tactics he uses to control Theon Greyjoy and Sansa Stark. Thanks to the protections of nobility given to him by his father, he is able to kill and maim with impunity. So he uses dirty tactics to defeat Stannis Baratheon's army and wages a war against Jon Snow, which he loses thanks to Sansa's last-minute deal with Lord Baelish and the knights of the Vale.