It’s the third DLC for Season Pass holders, available separately as well.
Let’s start with a teaser video for the expansion that is the last part of the season pass offer:
As this is a teaser, not much is revealed. But thanks to earlier data mining and some perceptive players, it’s believed that it will be a PvP mode in Domination style (“Fortification has been enabled at Alpha”). Two teams (red/blue) are visible in the video.
The full reveal is scheduled for today and you can watch it on Twitch at 8AM PST / 11AM EST / 5PM CET.