https://www.gamespot.com/articles/free-steam-game-now-available-for-a-limited-time/1100-6457987/

The acclaimed strategy game Crusader Kings II is currently free on Steam for a limited time. And to be clear, this isn't a "free play weekend" kind of thing. If you download it now, you get to keep and play it forever.

This is a good thing, because Crusader Kings II happens to be terrific. Released in 2012, this colorful game puts you in charge of a European kingdom in the Middle Ages and asks you to expand your power in any way you choose. You can advance your position using war tactics, diplomacy, scheming, or a combination of all three.