[Module] Legendary Potential Rarity

Also:

Once an item turns Legendary, you can only use Master Miracle Cubes on it.

Just like the normal cubes, you get a Master Miracle Cube Fragment when you use one. You can trade in 10 for a Silver Stamp, which adds a third line to a 2 lined item at a 50% chance, 20 for an Advanced Item Enhancement Scroll, or 30 for an Epic Potential Scroll, which can be used on a Rare item to change it to Epic.

from http://orangemushroom.wordpress.com/ which i now use since Spadow is gone