As of April 2012, all Imperceptible Beauty armor pieces can ONLY be purchased individually during City Festivals from the 1st - 7th each month. They can no longer be purchased from the NPCs at the mage towers.
These armor pieces give the look of bare skin, with the exception of the Breastplate and Loincloth. Equipping the Breastplate will only give male characters a truly bare chest. The Lioncloth will reveal the "underwear" all characters have by default. For male characters this displays ragged looking pants and a ragged skirt for females.
The armor in this set is for appearance-only and has no stats. See the Appearance gear page for an explanation of how to equip these items and a list of alternate crafted and quested gear that has a similar function.