The Dark Labyrinth

Consciousness makes an unwelcome return as you awaken, freezing and numb on cold stone. You are completely disoriented: the room is pitch black and your head throbs from whatever knocked you out. After a few minutes of fumbling around you are able to locate a torch and striker, the flare of light blinding you as it ignites. A few moments of painful blinking adjusts you to the light and you can properly survey your surroundings.
You seem to be in a holding cell of sorts, a dense iron door walling one side of your prison. The other wall is something of a mystery: it simply isn't there. Your cell seems to open into some kind of large shaft, continuing up and down into darkness. It looks like it might be an elevator shaft and you consider that this was likely how you were delivered here. You cringe inwardly as you realize you almost stumbled into the shaft when you were searching for a light. The fall would have surely killed you.

The walls of the shaft are almost perfectly smooth and a sheen of green slime makes it obvious you can't escape that way. Turning to the metal wall you give the door a closer examination, the locking mechanism looks formidable, although... wait a minute.
You give the door a solid push and the iron swings open soundlessly, its hinges well-oiled. You eye it confusedly for a moment before it slams shut with a deafening CLANG, echoing in the shaft behind you. It seems to be weighted and after a moment of consideration you realize it probably only opens from this side. There's really nothing else in the cell, just the torch and striker. It seems you only have one way forward.