https://www.gamespot.com/articles/free-xbox-one-and-360-games-with-gold-titles-of-de/1100-6455319/

We're now well into December, and that means Xbox Live Gold subscribers have the first of the month's free Games With Gold titles to claim. Two more games are available to download for free right now if you're an Xbox Live Gold member, with another two set to arrive during the second half of 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 and play it on their console. Take note that Child of Eden is only available through December 15, as Xbox 360 titles are only available for half of the month.