I know that I am supposed to do something with the 3 or 4 fountain looking things in order to kill him but I see no way to interact with them. I can't harm them and I can't click on them to interact.
try walking close to the plinths and hovering your cursor over the larger bowl at the bottom, it should change to one of the 'open bag' symbols you get when you hover over crates/chests etc.
then open it - you'll see why.
do this to the rest of the plinths
then open it - you'll see why.
do this to the rest of the plinths



