The door is just past a trap door that opens and closes every couple seconds, next to a teleportation field also appears and disappears. I can get past this obstacle, but the lever does nothing. How do I proceed past this puzzle?
As usual, the act of typing it all out makes me think of another couple things to try. I had not noticed that there was a pressure plate behind the grate to the left; placing something on that plate quickly before the floor fell out opened the way to a second lever and the solution; both the left and right lever were necessary to open the way.