You go forward down the passage for quite a long while...

After what seems like an eternity, you seem to notice the slope of the passage getting steeper, as if it was beginning to go downhill. In fact, the decline gets steeper and steeper the further you go. Before it becomes what you would deem "too steep to walk on without falling", you slip on an oily patch that you could not possibly have seen in the dim light. Your wild slide into the abyss begins...

...and ends abruptly on iron spikes some 100 feet below.