CK3: Royal Court announcement trailer:

Kings & Emperors will gain access to the Royal Court, a throne room where their loyal subjects can gather, where glorious artifacts can be put on display, and where the ruler can Hold Court in order to deal with the troubles and wishes of the realm. Similarly to medieval rulers of old, you can aspire to have the Grandest court in the world, or perhaps simply live up to the expectations put on you by your peers - no one respects a stingy monarch!

With the Royal Court, we want to immerse you in the life of a medieval ruler by letting you take the reins and experience rulership first-hand. You’ll not only see your ruler occupy the same space as your family and subjects, but you’ll have the opportunity to engage with many new and exciting systems - sponsor projects, spend gold on lavish amenities, solve strife between squabbling courtiers, appoint jesters, and much more! How will you rule your realm?

And what is a ruler without subjects, their people? After all, it's they who pay the taxes! Much like with faiths, cultures will be made more interesting and malleable - all in line with our vision of Player Freedom and Progression.

Different cultures will have different traditions, different opinions of each other, and even shift and change with time. No longer will cultures be static and similar - we want to give you, the player, the freedom and possibility to shape your own culture and guide its progress in a variety of exciting ways. Of course, culture will change at a slower pace than Faiths do - it’ll be gradual over time, tradition by tradition. Though sometimes larger shifts can occur due to isolation, or as the result of two different cultures intermingling.

Grow the acceptance between cultures in your realm, diverge your culture to adopt a new Ethos, or create a Hybrid between two cultures in your realm - adopting the language, traditions and aesthetic choices you find the most compelling. There are many possibilities to explore, and no two games will ever look the same again!
CK3: The Royal Court - The Vision | Paradox Interactive Forums