Converging Paths

Needs Royal Court or Khans of the Steppe (hybrid cultures come with either). Instant route: Ivar the Boneless of the Isles, 867 Wrath of the Northmen - he qualifies at game start. Open the culture window, Establish Hybrid Culture, pick your traditions, pay up. In general you need counties of both parent cultures in your realm and decent acceptance between them (the cost falls as acceptance rises), and the child culture inherits all innovations of both parents - which is exactly why Beacon of Progress runs on hybridisation.