https://www.polygon.com/2018/4/6/17206700/crusader-kings-2-free-download-steam

Crusader Kings 2, the acclaimed 2012 strategy game from Paradox Interactive, is free to download on Steam until 1 p.m. ET on Saturday, April 6. This is a free, permanent copy to keep, not a trial. The grand strategy game is available for Windows PC, Linux and Mac.

After the giveaway is over, Crusader Kings 2 will be offered at a 75 percent discount. The freebie appears to be tied to promotional bundles, each offered at discounts ranging from 27 percent to 58 percent.