Consolidation of power in Viking Age Scandinavia. Kings took power from multiple jarls, integrated different Norse peoples under their rule, and set up dynasties, starting the Sweden, Norway, and Denmark we know today. In BT, this could be done at the planetary level. Some Chaos March worlds described as having multiple factions in that sourcebook were good candidates. Similar historical arcs played out earlier with the Franks, culminating in Charlemagne, and at different stages in Britain with Alfred the Great and William the Conqueror.
Securing trade routes from Sweden through Slavic territory to Byzantium and Baghdad by the Rus (Swedish Vikings) during the Vendel and Viking Ages. The establishment of trade posts like Kiev and Novgorod along the Volga and Dnieper Rivers, and the consolidation of the surrounding Slavic tribes laid the foundations of the Russian state. In BT, this could play out over several worlds along a key jump route as a mercantile interests take over planetary governments (maybe using mercenaries where necessary) to link valuable resources and/or population centers.
The establishment of Norse buffer states during the Viking Age. After suffering years of raids and paying bribes to Viking raiders not to return, British and French rulers either accepted the Danelaw de facto or gave Viking leaders title and territory like Normandy, with the expectation that these buffer states would absorb or defend British and French territory from further Viking raids and invasions. The Romans did the same thing with various Germanic tribes in earlier eras. In BT, this could play out on almost any House border with the Periphery that is plagued by bandits.
Multi-generational feuds between families in Iceland and other Norse colonies. This is the stuff of many Icelandic sagas and is reflected in the larger Norse culture in legends and myths like Nibelungenlied. Think Hatfields and McCoys, only longer waits for more poetic vengeance. In BT, this could happen between feuding nobles and their house guards on any minor planet largely ignored by the ruling House or regional government. The ruling families of various Italian city-states undertook similar feuds that usually involved trade and mercenaries, made most famous in Romeo and Juliet.