The Black Market is a feature under the equipment tab that will offer various Limited Edition items that are no longer in regular rotation. Maybe you want to stock up on something that was issued back in the beginning of the game, or just get 1 item to help fulfill an achievement. The Black Market will tell you when the item leaves the market, "LEAVES (X) DAYS/WEEKS FROM NOW!". Unlike regular LE items, these do not have a limit capacity where it says there's less than X amount remaining. You can purchase as much from the Black Market to your hearts desire and don't have to wait for an Admin to refill it.