The Vhaerunite Piwafwi is forged by male priests of Vhaerun and given to, and only to, male Drow Infliltrators.  It is not a unique item, and is used by Drow Infiltriators in all cities where Vhaerun is secretly worshipped.
 
 

The Vhaerunite Piwafwi is either made for a specific male Drow Infiltrator, or passed down by his mentor.  The latter is achieved only by the student finally becoming the teacher and killing his mentor.  For a male Drow Infiltrator to take on an understudy is to specifically train him to do so.  
   The Vhaerunite Piwafwi owned by Tathlyn Tlintarn was passed down to him in this fashion, as he had to slay his own father to obtain it.
 

Abilities:
 
The Vhaerunite Piwafwi functions as a cloak of protection +3 in all aspects.  The wielder is also immune to creatures from the Demi-plane of Shadows.  The wearer is also immune to divination detect spells targeting him, such as Detect Magic, Detect Poison, Detect Evil, Detect Invisibility, Detect Charm, Detect Lie, and Detect Scrying. 
 
The Vhaerunite Piwafwi functions as a normal Drown Piwafwi, granting bonuses to the Hide in Shadows thief ability.  In addition, the wearer can cast Alter Self on himself up to 3 times per day.