Pictured: that astrolabe that surrounds the Westerosi sun.
An early artist’s conception of the astrolabe.
House Targaryen conquered Westeros three hundred years before the first episode of Game of Thrones takes place. The dragons they brought with them from their ancient homeland helped Aegon the Conqueror forge the Iron Throne from the swords of the lords they conquered. For three centuries, those dragons kept the Seven Kingdoms under Targaryen rule — and then the dragons died out.
Two decades before the first episode takes place, a Targaryen prince kidnaps Lyanna Stark, the fiancée of Robert Baratheon and sister of Eddard Stark. After Eddard’s father and brother are murdered by the Mad King Aerys while petitioning for her release, the Starks and the Baratheons rise up in rebellion against the Iron Throne. House Lannister joins the rebels late in the war, sacking King’s Landing and killing the last Targaryen king and his family.
After the death of the Mad King, Robert Baratheon claims the Iron Throne by virtue of a distant Targaryen ancestor. With his fiancée Lyanna Stark murdered during the war, King Robert marries Cersei Lannister to secure his reign and names Eddard Stark as Warden of the North. The last Targaryen children, Viserys and Daenerys, escape overseas into exile. Peace returns to the Seven Kingdoms at long last.