https://www.gamespot.com/articles/december-2017s-free-xbox-one-and-xbox-360-games-av/1100-6455319/

It's officially December around the world, which means Xbox Live Gold subscribers can now pick up the first of December's free Games With Gold titles. Two more games are now available to download for free if you're an Xbox Live Gold member, with another two set to arrive later in the month.

On Xbox One, Warhammer: End Times - Vermintide is free all month long, while Child of Eden is the freebie on Xbox 360. Note that this title plays on Xbox One through backwards compatibility, so you Xbox One owners can grab it as well.