General

Having trouble with occult cube

So I got an occult cube from a root abyss a few days ago. The problem is I can't use it. First thing I did was double click it, that did nothing. So then I decided i'd just drag it onto the piece of equipment I wanted to use it on. A message popped up saying, "Cannot be used on this item" even though the item had an epic potential. I then tried to use it on other pieces of equipment with rare or epic potential. No matter what the equip was, the same message popped up. Am I doing something wrong? Please enlighten me.