https://www.polygon.com/2018/9/19/17880036/destiny-2-gambit-free-trial-date-time

Destiny 2 developer Bungie enabled a free trial for its new Gambit mode the weekend before Destiny 2: Forsaken launched earlier this month. For players who missed out the first time, the Gambit free trial is coming back Sept. 21-23. This time, however, all of the enemy races and all four Gambit maps will be available in the trial.

For those not in the know, Gambit is Destiny’s first PvEvP mode — mixing both player-versus-player and the traditional player-versus-AI that the series is known for. Two teams of four each drop into a mirrored version of the same map. The teams must fight through waves of enemies, collecting a currency called Motes that drops from their foes. The first team to earn and safely deposit 75 Motes in their central bank will summon a boss that needs to be killed. Killing that boss ends the round, rewarding a point to whichever team killed the boss first.