Your eyes adjust slowly to the gloom, while you choke on the falling silt-laden dust. An unwary step causes rumbling threaten above, the dark stone ceiling looking overburdened by the mountain above it. If you skirt around the edge of the room, you may be able to prevent finishing what weather and time could not.
Dark eyes pierce the darkness, watching you. You can imagine seeing hackles rise and teeth be bared, but only when you hold your breath and listen closely can you hear deep growling. The beast seems constrained to the center of the room, but that earns you no relief as you complete the circuit and find no passageway to the rooms beyond.
You could leave the way you came in and search for another access, or try to approach the center of the room and hope to expose a secret door. Surely, given the apparent state of this dungeon, you could find an exterior collapse that would lead invite you into deeper halls.
Stay and approach the center - OR - Look for another way in