Forges came in with the black armory DLC, these forges are quite the grind to unlock let alone complete. to unlock the first forge you must calibrate the machine gun frame by killing multiple enemies with your power weapon and other steps but once you’re done with it you are able to hop into the forge and join two others because it ain’t easy to do.
the first wave you just through batteries at it willy nilly until you hit it with 20 batteries. by the way you can get these batteries by killing blowing blue enemies, small glowers=1 battery big glowers=2 batteries.
once you make to the second wave the glowers are bigger and harder to kill along with the other adds, the forge also becomes harder to hit with batteries because now you have to aim at the middle of the forge or else you’re batteries just bounce off.
once you’re at the end you’ll have to kill this bullet sponge, after you shoot his drones to take his shield off that is and then you’ll be done and get your weapon.
Destiny 2 