Ok so the after beating the ogre you are going to keep proceeding toward oryx. Once you get to the part where you have to move along a ledge while there is these booby tarps that shoot out of the wall and try and knock you off. So when you get to this part you will turn right out of the door you came out of. Pull your ghost out and look for the invisible platforms to jump to the other side. Just keep following them over and up and it will lead you directly to a chest