Larian Studios Forums Divinity 2 - Ego Draconis (English) Help/Tips/Tricks After i kill Ba'al need help opening door?

In the dungeon cave area where you kill Ba'al you get a lever, what is it for? There is also a door like a prison cell door I can't open. Does that lever open the door somehow? I searched all over and can't find anything to put that lever in or to open that door?

lever will open secret door at the far end of mines if i remember correctly

Where do i put it? I looked all around that door, i must be missing it?
Thanks for the help though.

Really enjoying this game.

There is a small socket for the lever on the ground in the far eastern room.