https://www.pcgamer.com/galactic-civilizations-2-ultimate-edition-is-free-in-the-humble-store-spring-sale/

The Humble Store Spring Sale has now been underway for about a week, and that apparently means that it's time for a new free game. For the next two days, Stardock's Galactic Civilization 2: Ultimate Edition, which includes the base game and the Dark Avatar and Twilight of the Arnor expansions, is yours for the taking if you want it. 

Galactic Civilizations 2: Dread Lords was originally released in 2006, but the great thing about strategy games is that as they get older, they tend to get better: The graphics will obviously be dated, but updates and expansions can mean significantly better experiences may be had years after a game first comes out. In fact, GalCiv2 got a surprise update in 2015 that made major improvements to gameplay, races, and AI, and even tuned up the graphics a bit.