I NEED HELP.......i have taken control of the companions and i took some work.i was sent to recover a mace in a cave but i can only go so far then i reach a waterfall thats to high to climb-a dead end.there is another place it says i can go to a darwen ruin.when i get there there is a strange floating ball in middle of room when i touch it a cage comes up and the ball floats around the room then the floor dissapears and i fall down a huge void!!!

any ideas please ......its doing my head in

I believe that is one of the paths into Blackreach.