If you're not interested in Stellaris' version of sci-fi and space stories, you can replace them with the Warhammer 40,000 ones.
Stellaris, the latest grand strategy game from Paradox is breaking sales records. Being a Paradox game, mod support is one of its greatest assets, and it's already received its first big one.
Twilight of the Imperium is a mod created by Panther, who's had a hand in making various other mods for Paradox games. The mod, as you may have guessed from the name, brings the world of Warhammer 40,000 to Stellaris.
Although still in early stages, the mod already has great features such as aligning the various races with Stellaris' in-game systems like home planet, ethics, traits, and forms of government. As for races, the usual suspects are all here, including Chaos and Tau.
Here's YouTuber Serious Gaming showing it off.
You can download and learn more about Twilight of the Imperium through here.