Before the v3.1.0 specific tweaks, the base expansion introduced several game-changing systems available on the Crusader Kings II Wiki:
Tribal Pagan rulers can now seek a sponsor from an organized faith (like Christianity or Islam) to convert their entire realm at once, bypassing the slower province-by-province method. [TOOL] CK2 Holy Fury Map Generator - Paradox Forum Crusader.Kings.II.Holy.Fury.Update.v3.1.0-CODEX...
The prestige requirement for the "Forge Bloodline" ambition was increased to 15,000 , and the spawn rate for legendary lineages like Alexander the Great or Ashoka was reduced to maintain their rarity. Before the v3
Pagan characters can join exclusive martial societies to climb ranks, unlock powerful combat bonuses, and call upon spiritual allies. If using the "Random World" feature, players can
If using the "Random World" feature, players can use specialized map generation tools to further customize their seeds.
Most features can be tested or managed via the Console Commands (typically opened with the ` or ~ key).