opening the black chests

In the toize valley mines,when you smash the Bacura with the rock,examine the desintagrated parts of it,you will find Colette's darkness weapon called evil eye.Then with the Rheihards go to Flanoir and go in front of the store that is never open.There will be a guy with dark blue hair,he will say a couple of things and he gives you The Nebilim (Lloyd's darkness weapon)and the Nebilim key.The Nebilim Key allows you to open the black chests.