Canute the Greater

The trigger is the DECISION - "Secure the High Kingdom of the North Sea" - and you must be tribal and unreformed when you take it; forming the empire any other way doesn't count (there are confirmed reports from players who found this out the hard way). The decision wants England, Denmark and Norway held for 30 years within ONE ruler's lifetime, so: play a son of Ragnarr from 867 (Ivar, Sigurðr or Björn snowball fastest), conquer the three kingdoms young, then keep that ruler alive - Whole of Body perks, good physician - while the clock runs. Do NOT reform Asatru and do NOT go feudal at any point; either permanently voids it. Overlaps heavily with Blood Eagle territory-wise.