Skarghash continues forward down the slope, with Taviss, Ari, Khalia, and Jango following behind. About halfway into the tunnel, all five of you begin to notice that the temperature begins to warm up. It is easily bearable, but the further you walk, the warmer it does get. After sixty feet or so the passage turns sharply left and doubles back on itself, travels forward another forty feet or so, and then banks to the right. As you've continued walking, the air has kept getting warmer, and the tunnel has kept sloping down deeper.
After curving around to the right, Skarghash stops short. You all look and see before you a set of steep stairs dropping before you. The heat has risen quite a bit by this point, and while it is not hurting or anything, it is becoming slightly uncomfortable. Like being in a sauna.
Skarghash takes a few moments to examine the staircase, and he determines that while each step is steep (maybe 14 inches high and only 8 inches wide), if you all take it easy and carefully, you should be able to make it down. The five of you help each other out as you slowly decend the thirty or so stairs
(Balance checks Take 20s *success*) and at the bottom it opens up into a huge circular dome-like cavern.
From where you stand at the base of the stairs, you do a quick inventory. The room is a dome maybe forty-five feet across and twenty-plus feet high... the walls and floor are smooth, flat, almost obsidian-like in appearance. This is a marked difference from the tunnels you've been walking through, as you don't need to be a dwarf to see that this place looks "finished". You notice that at a dozen points around the room there are passages maybe four feet high that are blocked off by metal bars. Finally, in the center of the room there is a crystaline rock formation growing up from the floor, also mainly of the same obsidian-like appearance as the walls and floor.
You do not see or hear the pirates here at this moment.