I'll give a brief bullet-point overview of the CK2 campaign as alt-history to explain the general gist of things:
- A Karelian chief fancies himself a bad motherfucker and goes around conquering neighbouring tribes under his banner, starts a big long feud with Rurik, which ends with Rurik's premature death in an ambush (obviously nationalistic historians would claim single combat and epic battle, not cunning).
- The following destabilization of Rurik's realm leads to fracturing and eventually the Slavs being driven back further South.
- Norse jarls launch an invasion of Kullervo's realm, but are repulsed with great cost.
- King Kullervo I dies after having created the first unified Finnic state around the baltic tribes.
- Pagan wars rage in the North and East for centuries, and the heirs of Kullervo rally Mordvin and Permian tribes against the remaining Slavs, along with repelling two additional invasions from the Norse.
- In early 10th century, a great army of all the Finnic tribes across Europe assembles and marches down to Slavic lands. Slavs are driven to the Black Sea.
- Following the utter devastation of the Slavs, the Seljuks invade Europe. As Cumans fleet to Bulgaria and Caucasus from the Turk horde, Finns join the defense as pre-emptive security measure and assist remaining locals in revolting against the Turk horde.
- With the Turkish threat gone, Finns turn their attention to exacting revenge on the Norse heathens that have long been their enemies. A series of wars drive the Norse further and further into the mountains.
- The growing threat in the Baltic North attracts papal attention. Three crusades are repelled and retributive raids and campaigns drive out Christian coastal populations around the Baltic.
- The dread Mongol hordes arrive across the Urals, and the Finns mount their defense. The united tribes break the Mongol advance in the Ural Mountains in a series of battles.
- The Norse, being pushed further and further back by the advancing Finns and out of their old homelands, turn to their Fylkir, a great holy man.
- Jomsvikings form the core around the Norse fortress-state, ensuring the survival of their culture at the edge of the North.
- The Fylkirs see that they cannot remain forever on the last fjords and among rocky islands. Stories of Vinland inspire the Norse people with a promised land beyond the sea.
- Lithuanians form small, loosely knit tribal fiefs, which expand inland as Slavs retreat.
- Lithuanians eventually unify and due to the unsuccesful Crusades to the North, sees no reason to become sworn enemies with their other pagan neighbours.
- Lithuanians assimilate the Baltic tribes leaving the coastal areas as the Finnic Livonian tribes never depopulate.
- Byzantium falls into disarray as the Orthodoxy crumbles around it. A Greek Sunni convert gathers a warhost and seizes Constantinople, proclaiming himself the Sultan of Anatolia.
- Anatolia remains a regional power for several hundred years, until the catastrophic Great Civil War tears apart the Abbasid Caliphate.
- In the disarray, Anatolia emerges as the dominant Islamic state.
- Abbasids retain a foothold in Baghdad, but the Caliphate is forever lost.
- In 13th century, a Christian king ascends to the throne of Egypt, and an alliance with the Nubian kings leads to a series of wars where the Islamic lands are divided in two. Alexandria becomes the center of the remnants of Orthodox Christianity.
- Nubian kings drive out Bedouin warlords from Ethiopia, forming the Holy Abyssinian Empire.
- During the last great strife within the Muslim realm, Zoroastrians rise up in Persia as Timur invades. Against all odds, the fanatic armies of the Shaoshyant drive out the Iron Khan, and Ahura Mazda is once again praised across Persia.
- The Shaoshyant is decreed the true Shahanshah of the Persian empire. A great wave of conversions change the face of Persian society.
- In 11th century, Mali unites under a great Mansa, and the African horde strikes hard at the Berber states. Juju is deemed strong.
- Andalucian Sultans crush Castilians and conquer almost all Spain in 9th century. Only the Basque king of Navarra resists.
- In 11th century, the Basque achieve a great defensive victory, and shatter the Andalucian armies. Basque come to dominate the Iberian peninsula.
- Karling dynasty rules Central Europe uninterrupted for generations. The Karlings of Italy and Burgundy unite, forming Burgundy-Italy.
- Burgundy-Italy remains the decisive actor in European politics, wielding unparalled wealth and power in the West.
- In the 12th century, rebels and rival kingdoms unite against Burgundy-Italy, and they are driven out of Southern Italy and Hungary.
- The Bavarian Karlings come to dominate German politics, forming Greater Bavaria and crushing any ideas of elective monarchy among the German states in favor of their own centralized power.
- The Lotharingian Karlings maintain balance between Francia and Greater Bavaria for centuries, losing ground only to regain it later.
- A Transylvanian count claiming descent from Arpad dynasty assumes leadership of the Hungarian resistance against Italo-Burgundian domination. Striking an alliance with Bavaria and Lotharingia, the Karlings are driven out and Hungarians regain their indepedence after three hundred years.
- Cumans fleeing the Turkish horde form Tartaria in former Bulgaria, their horse refugees routing their opponents. The Khan converts to the Christian faith, gaining protection from his enemies.
- The once-great kingdom of Georgia falls to Saracen Jihad in the 12th century. As the Georgian sultan arranges his realm, the Orthodox population remaining falls under the protection of the Cuman armies hiding among the mountains.
- This area is added to the empire of Tartaria, but Georgian Sultanate maintains its legitimacy and hostilities flare up repeatedly over the centuries.
- A Welsh adventurer has a stroke of luck, and seizes the vacant throne of Scotland during civil unrest.
- The first Lleynn king returns home, and assumes the Welsh crown as well.
- The Lleynn rule sees Welsh rise to dominate Britain, Ireland and Brittany falling under their aegis as the Anglo-Saxons repeatedly lose ground in bloody wars.
- The alliance between Godwins and the Great Heathen Army seals the fate of William the Bastard, and Anglo-Saxon pagans hold power in English court.
