I was running around patrol on Nessus, and discovered that when I entered the Prodromus Down area from Exodus Black, the energy barriers from the strike went up behind me. I was unable to continue to the next area either, as there is another energy barrier at that end. I haven't found any buttons or anything to interact with yet, nor have any enemies spawned. I did, however, find a strange room beneath the normal path. If you continue down the stairs, take the left, but then immediately take another left, you'll find yourself in a room with a slope on the close right corner, leading down to the hidden room. All that I could find within it was some debris and two Vex corpses. I've spent too much time here sniffing around, but if anybody else wants to check it out, post if you find anything. Tl;dr Got sealed into Prodromus Down on Nessus and found a hidden room.