Trials of the Nine is Destiny 2’s competitive endgame activity. Trials runs during the weekend, starting Friday and ending at the weekly reset on Tuesday morning.
This week, Trials of the Nine is Survival on Altar of Flame.

Trials of the Nine is a 4v4 activity but is not matchmade, so you will need to bring in your own four-person fireteam. Each weekend, the map and mode for Trials will rotate to present new challenges for players, but will remain the same single map and mode for the duration of the weekend so that teams can work out strategies and learn the call outs. Other teams will be doing the same, so prepare for some tough fights.
To access Trials of the Nine, players must complete the Destiny 2 campaign, finish Shaxx’s Call to Arms milestone at least one time, and be a power level of 260 or greater.
Players must complete the Destiny 2 campaign, the Call to Arms Milestone at least once, and have 260 Power for access to Trials of the Nine.
? Bungie Help (@BungieHelp) September 15, 2017

Loadouts are locked for Destiny 2 Trials of the Nine, so make sure you enter the activity with the weapons and subclass that you intend to use. You won’t be able to change them mid-match. Level advantages are disabled, so don’t worry if you don’t have the best endgame gear. Just go in with weapons you feel comfortable with. This makes Trials more about individual player skill than powerful gear.
Trials can be started by gathering a fireteam of four ...