ROBERT ADAMS and THE HORSECLANS
Robert Adams was a former military man who chose to write an epic tale of rebuilding life after an enormous disaster. Some people survived, and responded by trying to reestablish "society". Others used the disaster to choose to gather in tribes, and take up arms. Some groups chose to develop religious villages, some chose to live isolated as possible, to avoid the wandering violent tribes.
But the most important tribe or clan as they are referred to by Adams, were the Horseclans. They were led by heroes of expertise in weapons, and legendary skills, but they had been changed too, said to be perhaps immortal.
The Horseclans can be played with two wonderful books in the Gurps world, and various editions of the game GURPS from Steve Jackson Games.
The books that I have read, shown here, have covers by Ken Kelly, but the new editions are different. I am happy with mine, and the writing is very much worth an afternoon or evening when the winds are cold, the snow is falling, and you have a quiet night waiting.