Ridylls of the King
The year is 490 AD and confirmation has finally reached the shores of Brittania that a Barbarian has crowned himself emperor of Rome. It’s been more than fifty years since the Ninth Legion formally withdrew from the shores of the Isles and left the peoples to their own fates.
It has not been an easy half century. Wars between the native Brittons, Angles and Picts, and the remains of the Ninth Legion and their ethnic Roman brethren, have, until recently plunged the Isles into war and chaos. Fifteen years ago, however, a young warrior, raised by the Ninth and dedicated to the advancement of the Brythonic peoples, proclaimed himself High King of Brittania and has served his people faithfully ever since. His name is Arcturus Aurelianus Draconis, Legatus of the Ninth, Heir to the Pen Draigh. But shadows are deepening again. With the dissolution of Rome, the Saxons have proclaimed a new Emperor Lucerius who means to take Albion for his own. And with the Angles having thrown in their lot with the Saxon invaders, the Pendragon’s rule is perilous, on the brink of collapse.
After that, take a look at your wiki. There is some more helpful info there.