I have owned this game since just after I graduated college four years ago. I played it relentlessly, I have bought all the downloadable content (DLC) which have radically altered the game. It is a mildly amusing to think about the earliest versions of this game and how I would find them unplayable. I stopped playing about two years ago, right after the release of the Rajas of India DLC, which added the Subcontinent and all that entailed. I burned out a bit and I moved on to other games. But I have recently got back into the game, thanks in part to the fact that a good friend of mine who has merely 500 odd hours in CK2 were able to finally play a bit of multiplayer together. The game as it is originally premises is you are a Catholic feudal lord somewhere between 1066-1453 and you have to manage your dynasty through those centuries. No built-in goals, a few failure conditions and a “drown less swim lesson” tutorial.
It now is far more. You are someone of some importance from 769-1453 who can be a Christian (Catholic, Orthodox, Miaphysite, Nestorian and their heresies), Muslim (Sunni, Shia, Ibadi and heresies) Jewish (with Samaritan and Karaite heresies) Mazdan (Zoroastrian and the heretical Manichaean, Mazdaki) Pagan (Germanic, Slavic, Tengri, Romuva, West African, Zunist and Suomenusko) or Dharmic (Hindu, Buddhist and Jain) who can be a Feudal lord, Islamic Iqta ruler, Nomadic warlord, Tribal ruler or a Merchant Republic Patrician. And that is just what you can actively play as the player. The AI is running things like feudal barons, landed priests, mayors of cities, theocratic realms, inland republics, mercenary captains, adventuring characters, holy orders, the Catholic Papacy, The Orthodox Ecumenical Patriarch, the Miaphysite Papacy, the Nestorian Patriarchy of the East, the myriad and sundry heresiarchs, random idiots, witches of the wilds, the spawn of Satan, inbreeds, murderers, petty courtiers and many others.
Sound daunting? It is very much an unwieldy and creaky system but it has so much fun buried in there.
I have two games that stand out in my memory:
The most Catholic dynasty of de Santiago, the Emperors of All Spain and Francia, Kings of Italy, Sicily, Jerusalem Mauritania, Africa, Egypt, Syria, Cyprus and France, the suzerain of the Papacy and countless other titles. I took this dynasty from 867 till 1453 and rose from the King of Asturias and proceeded to create this feudal superstate that was almost entirely the personal property of my dynasty. I dominated the Papacy, lead crusades, created the Empires of Hispania and Francia, and even managed to get my dynasty to become Sayyids, which in game is just a small (+5 on a scale between -100 to +100) diplomatic bonus to Muslim characters. It involved getting an Empress elected to the throne of Hispania, a fortuitous exile of an Abbasid son and some bribes. I had a son who I dumped into an Archbishopric and get elected to the College of Cardinals and eventually the Papacy without my input beyond making him an Archbishop. He was not entirely happy with the fact that I ignored him from the age of six until he became Pope. Such is the way of this game
The unrepentantly Germanic pagans of the Norse Yngling dynasty, who reformed the Germanic religion to counter the spread of Christendom. The Yngling Fylkirs reigned as veritable emperors over the Viking world. Viking hordes ravaged the shores of the known world. All of Scandinavia, the British Isles, northern Germany, Rus and the Baltic were ruled by Yngling kinsmen. For a short time even Mauretania in North Africa was ruled by a Viking warlord. It was comical, I once sacrificed the Pope during a Blót. Catholicism collapsed against the onslaught, only the Orthodox church protected by the rump of the Roman Empire in Byzantium survived. In the end I got bored as I had destroyed everything before me, my stranglehold on power was unassailable and at one point I was pretty sure that 1 in 3 characters in game (there are usually thousands of characters that each have desires, ambitions and plots) were somehow related to me either as Yngling kinsmen or descended from a Yngling. The inbreeding reached dangerous levels when I looked and had five generations of Fylkirs (the dual secular-ecclesiastical title held by my family) all had consanguineous grandparents. Never hurt the mainline of the dynasty but I heard things got real weird in Iceland and the British Isles. So I quit and abandoned that game.
Those two examples of games that I vividly remember. I did not include some fun massacre-y bits, like when I overthrew an entire branch of the de Santiago dynasty for treason or killed an entire Norse clan because their chief killed a young daughter of Fylkir Gandalfr I Haraldrsson Yngling. The game goes to strange places and does strange things.