Anbennar is a sprawling fantasy mod for Europa Universalis 4 (opens in new tab) that has been in the works for years. It's a passion project that started as translating one guy's homebrewed D&D fantasy setting into a playable mod, but has grown far beyond those origins into a multi-author shared world—and one of the most impressive EU4 mods out there. It's a total conversion, utterly remaking the game as a fantasy world complete with fictional continents, nations, governments, species, and religions.
The latest update, called Of Gods and Gears, adds systems for crafting works of magical Artificiery, and a religion based around that. It also adds Vampires, and a set of missions for vampiric rulers. It uses new mechanics for EU4 to rework how Orcs hold territory, and how adventurous humans try to conquer it and forge their own nations. The update also adds new mission trees for several nations, emphasizing missions for Goblins, Gnomes, Kobolds, and a human guild whose mechanics are impacted by the addition of magical artificiery.
If Anbennar sounds cool to you, great news: There's a Crusader Kings 3 version in the works. In the meantime, you can find Anbennar for Europa Universalis IV on the Steam Workshop. For updates on the mods, there's also Anbennar on Twitter.