Paradox Development Studio is known for its grand strategy games that have largely the same gameplay but are spread about different eras of human history. Six years ago though it released Crusader Kings II and while you could still move about Europe expanding your empire and spreading your influence like most other grand strategy games, there was an expanded diplomacy and heritage system that perfectly brought in the best elements of the role-playing genre.
Ever since the game released, Paradox has been supporting the game through DLC and expansions that range from small things like unlocking new kingdoms to play as all the way up to the latest expansion which added an unplayable but still influential Chinese kingdom that changed how you played in Eastern Asia. Some people think the DLC plan is bad but for a chunk of Crusader Kings players, it is the only game they play so tossing another 15 bucks to the developers every six months isn't the worst thing in the world for something you love.
via destructoid https://www.destructoid.com/steam-is-giving-away-crusader-kings-ii-for-free-for-the-next-48-hours-497456.phtml