I've poured so many hours into CKII and even more into it with the A Song of Ice and Fire (Game of Thrones) mod installed. It sounds epic, but so too is the experience of playing through. A basic summary of the adventure would be: you're tasked with heading up a medieval dynasty and the goal is to keep it running for as long as you can - taking down enemies, forging alliances and engaging in wars along the way.
From the age of Viking raids to the fall of Byzantium, Crusader Kings III promises to take you on a journey throughout history.