Here with a black background to show the highlights effect
step 9 of 11
Add the background and mask the extreme of the blade
step 10 of 11
duplicate the background image dark it using Brightness/Contrast then apply some Gaussian blur, mask the stones to finish this step
step 11 of 11
Make the background and the shadows on the stones even more darker (now with brushes) to make the sword the centre of attention.
Some mystic lights used added to the background too.