Crusader Kings 3 Royal Court expansion brings with it interesting changes, allowing players to affect history in deeper ways than ever before. One of those is the cultural aspect of societal development.
War and commerce are not the only things one can ascribe to medieval times. Though sometimes called the Dark Ages, nothing can be further from the truth on a world scale. Cultures have blossomed, peaked, and wilted in the era Crusader Kings 3 encompasses, and the culture feature overhaul is a way for players to experience it all fully.
There are two ways for a player to create their own culture.
Hybrid cultures are one of those options. Players will be able to merge two cultures together to form a new one, albeit following some rules and fulfilling certain conditions. Buth cultures must be in a player's realm, and cultural acceptance must be present, as it makes no sense to create a new culture with recently conquered people.
Language, traditions, aesthetics, and martial customs are all things that can be mixed and matched according to the player's preference. Naming a culture is either left to the creator's discretion, but should the player need it, the game will provide names to choose from. One thing to note is that hybrid cultures cannot have the same roots, as then it makes more sense to use either of those, rather than combining them.
Diverging a culture is the second option that is available to players. Default names are based on the title the player has at the time of diverging, and there are fewer options to change. Languages will mostly stay the same, with aesthetics and military customs requiring players to fulfill certain requirements first. The defining factor of a diverging culture is in the cultural pillars, with at least one pillar having to be changed for a culture to be considered a divergent one.
Of course, not all culture changes are player-driven. In every playthrough, new cultures will emerge in a natural way, according to the history and borders being formed. These will be both hybrid and divergent cultures, based on the situation in the field, should weaker nations find themselves resisting a more powerful enemy, or a crumbling empire not looking to assimilate all their territories effectively.
The Royal Court expansion will bring with it a free culture overhaul, however, the creating culture feature will require the players to own the DLC.