At the beginning of season 7 of Game of Thrones, Daenerys Targaryen summons Jon Snow to Dragonstone to honor the pledge his Stark ancestors made to the Targaryens roughly three hundred years ago. That pact ended when Daenerys' father and the last Targaryen king, Aerys II aka the Mad King burned Jon's ancestors alive. As a consequence, the Starks called the banners of war to topple the Targaryens on the Iron Throne.