Because Destiny 2 Moon is a very strange place, you can craft weapons from Essence. The Essence of Rage will give you the One Small Step Shotgun, as long as you can clean it. To do this, you will need to find the Fangs of ShunGath. In this guide, we'll show you where to find them.
Destiny 2 - Location of the Fangs of ShunGath - World Grave
To get to the end of the world, launch into Eris Morn, get on your sparrow and head right towards the Anchor of Light. Go through the first right turn that would take you to the Fallen area and take the second smaller right turn. This will take you to the temple of Crota. Go inside, then continue to the room with the recessed metal platform in the center. Go to the back of the area and turn left, go down the stairs and turn right into the next room, then exit through the exit that will be in front of you.
Continue on this path until you come to the World's Grave. When you get there, go straight into the first room, then jump onto the platform at the end and go left. This will take you to the room where ShunGath is located.
Now they don't want to give up their fangs, so kill them and they'll end up in your inventory. After that, complete the rest of the Essence challenges or return to the lectern to collect your new weapon. Above is a video that will show you how to get to where you need to be in the World's Grave.
ShunGath isn't particularly difficult to kill, so you shouldn't have any real issues with it no matter your power level. Good luck, Guardian!