i tried trading a crystal to a telepoint but it told me that i should come back with an empty slot. i opened up atleast 4 slots and still i couldn't get the faded crystal.
Actually, you are wrong. It's also used in the Black Mage AF1 quest for the Casting Wand. You have to trade one to the ??? point in Xarcabard, then defeat the Chaos Elemental that appears (NM).