A brand new competitive mode, this will open up on October 11th and run through November 20th, new mode has a 7 v 7 format in Tier X only vehicles. If you participate you'll face players of equal rating. The whole mode will take place during the Season of the Griffin.
There are several rules to keep in mind, including that the matchmaker will select allies and opponents for each 7-person team based on the mode's ranked system. It will find opponents with a similar rating. All vehicles will have their own combat roles, and each role will have a role skill with 3 levels of charge that you can use to strategize and upgrade during the battle. The usual three-person platoons, you will have two players squads or you can create a team of 7 commanders and take on a super platoon on the other side.
There are two lines of rewards, the first one featuring a progressive 2D Style and the second featuring more traditional Rewards. If you participate in Onslaught you'll also be able to earn battle pass points. There are a number of other new mechanics, as well as a rundown in an official announcement on all the combat role skills and the ranking system.
You can earn Prestige points as you battle and the more actions you take that are relevant to your combat role that you are assigned, the more points you will learn. If you are team is able to capture points of interest you'll be able to unlock and activate tactical skills and gain an advantage for your team.