Beyond Light introduced a new Public Event to Destiny 2, the Fallen Brigs. This is quite a fun one, combining elements of the Darkness and the Fallen faction. The event revolves around three shielded Brigs, giant Fallen mechs.
A Darkness splinter will appear, with three drones flying around it. Shoot the drones, then capture the Darkness splinter by standing in the bright circle on the ground below it while the counter ticks down to free one of the Brigs. You then need to destroy the mech and move on to the next Darkness splinter.
The Brigs are tough to figher because the do a lot of sneaky area of effect damage. They will fire an explosive shell at you that sticks in the ground, then does huge damage a second or two later. The will also fire a group of rockets that will smash into the ground all around you, so be sure to dodge these.
You need to repeat this for all the other Mechs and splinters, and if you shoot the three drones each time, it will turn the event Heroic. This is where it gets a bit wild, as a huge Brig will spawn in. This thing is massive, and will take a lot of firepower to bring it down.