Note: Instead of making a proxy, please use Object > Library Override > Make after linking rigs into the scene (after this, you'll be able to access the controllers and switch to Pose Mode). Library overrides will snap objects back to world origin, but you can select the God controller on the sword (or the ‘sword’ controller if you like) while in Pose mode, press Shift+S and choose ‘Selection to Cursor’. This will snap the sword back to where you put the 3D cursor in the scene.