There's multiple pits and a button.
It would cause mayhem. He needs protection.
Check out the panel on the right side of the door. Interact with it.
Pry it off. ?
Use the crowbar on the panel.
You can test the room with it. Try to click the button in the middle.
Now, just choose wisely where the cage will drop. Drag the cage to some spot.
You can't block all of the pits with one cage.
Drop it on the button. Drag the cage on top of the button.
Leave the control panel and go click the actual button, the central device, between the pits.
Use the liquid nitrogen spray on the abomination.