Paradox Interactive's sweeping historical grand strategy title Europa Universalis 4 is the latest freebie to grace the Epic Games Store.
Released back in 2013 and still tottering along today (its most recent expansion, Leviathan, was so disastrous its director issued an apology), Europa Universalis 4 gives players control of a country somewhere between 1444 to 1821 and lets them shape it into global significance through trade, diplomacy, colonisation, and war.
It's a supremely complicated beast (I ended up watching ten hours of YouTube tutorials before I could even begin to fathom its depths and make sense of its interface), but the core game is a dazzlingly rich thing, full of enthralling strategic possibilities, if you manage to crack its shell.