To commemorate the sixth anniversary of XCOM: Enemy Unknown, Firaxis Games has released the XCOM 2: Tactical Legacy Pack, a free DLC for anyone who owns War of the Chosen on PC.
The pack includes everything from custom skirmishes, to daily challenge archives, to story driven missions that bridge the gap between Enemy Unknown and XCOM 2. In the archived stream here, you can watch Mike Mahardy and Erick Tay fight through several of those missions, and create a custom mission.
For more on XCOM 2, stay tuned to GameSpot - Mike will likely rave about it at some point, on any given video that has nothing to do with XCOM.