In our review of Crusader Kings 3, we wrote that one of the best aspects of the game is its sandbox RPG feel. Even though CK3 is ultimately a grand strategy game about conquering bits of the world and trying to fight off your rivals, it's remarkable how well CK3 forces you to care about the ruler you're controlling.
Events trigger about lost loves, missed opportunities, tiny triumphs, and, of course, very good dogs. If you're looking to expand on that aspect of the game, this is the mod you need.
VIET Events ((an acronym for "Very Immersive Events and Tales") lets you add to the stories in your headcanon, bringing with it a huge number of events (as of this writing, over 200) that flesh everything out.
These events are sometimes very small, touching on little things like an encounter with a stranger or a new experience with food, but sometimes they're massive, giving your character an entirely new outlook on life.
VIET is a wonderful mod for bringing the stories of CK3 to life.