Hey I have the same problem.
There is a leaver nearby if you come from the mansion it's on the right side.
But that won't help you much as you need a special panting in order to get into the last room.
And I have no idea were to find it
I did read this:
https://guides4gamers.com/divinity-original-sin-2/quest/hammerfall/Because of it I now have the 2 items needed (both stolen) to get through the Path of Blood but I don't get the amulet to work
