You can fight in the fog and rain of England, in the shimmering desert near Acre or Jerusalem, or you can run for your life from a Mongol horde on the steppes of Russia. The magnificent 1257AD mod covers all of Europe, and much of North Africa and Outremer in 1257, with opportunities to serve as a vassal of any of dozens of kingdoms, or as an independent mercenary or trader.
Especially looking for a Medieval Europe/England mod or one based around the Crusades.
