The Witcher has been around for a good while -- since the '80s in short story form and '90s in novelization form --but only recently did the series explode, creeping up into the zeitgeist with each main entry until it could no longer stay in its fantasy niche with Wild Hunt.
Since then it's spawned a spinoff in the form of Gwent: The Witcher Card Game, which CD Projekt Red has been heavily promoting in a fair weather era of CCGs. As part of a promotion on GOG you can grab a free keg (read: lootbox), but the real rub is that it comes with a free copy of the original Witcher.
It has some kinks that a decade and change game would, but story-wise it still holds up and manages to nail that old school morally grey feel.
Welcome Bonus [GOG]
via destructoid https://www.destructoid.com/the-original-witcher-which-is-still-great-is-free-on-gog-at-the-moment-500902.phtml