Half-drow are common in drow society. Many drow take human slaves, and children are born. Most of the time these half-drow become slaves in the various households, but sometimes they are left to die in the Underdark because of drow pride or due to some secret. Riggilla was born to a human slave in a prominent drow household that prided itself on the purity of its blood. Servants of Lolth for thousands of years, the family bred to keep its bloodline pure and connected to only the best "stock" in other families. When slaves became pregnant, as often happened, the children were either killed in the womb (often with the mother) or left in the Underdark to die. Monsters usually took care of these little messes for the drow. Rarely, such a child would be born and then handed over to a mind flayer ally as a gift.

Riggilla was left to die, but before any hungry monsters found her, she was taken by a raiding party of duergar that had been spying on a nearby drow fortification. The gray dwarves thought that she might make a reasonable slave, or that perhaps her loyalty could be turned against her own kind and she could be used as a spy or assassin. The dwarves informed her that they had purchased her from her family and raised her as a slave. As she grew older, they trained her in the quiet arts of thievery and killing, and they gave her more comforts. Though hating her own kind for selling her, she never stopped hating the duergar either. Eventually the dwarves saw that she was hopeless, from their point of view, and killed her. Or so they thought.

Riggilla's body was left in the Underdark for dead, but she somehow survived. She never talks about this period in her life -- if she talks about her life at all. She made her way to the surface and found that it was not as bad as the duergar had said it would be. After she was healthy again, she made her way to Telflamm in Thesk. There, she assumed the guise of a man (her build and facial features make this disguise easy for her) and got work with a mercantile company as a security consultant using the name Cosim. Her job was to make sure that no one could steal the wares of the company, and to find and silence any who did so before they could tell anyone. The work was easy, and she found she had time for some thievery on the side. Her employers doubtlessly knew that she victimized their competitors, but they never said a word. They even arranged for tidbits of information to fall into her hands that would help her and arranged for her to be off work at just the right times.

Her thievery eventually brought her into contact with the Shadowmasters of Telflamm, and "Cosim" became a member. She rose quickly and showed a great affinity for the shadows that caught the attention of the priests of Mask with the guild. She was persuaded to undergo the shadow-walker ritual, and then she was granted a higher place in the organization.

Now deep in the inner ring of the Shadowmasters, Riggila travels from Telflamm to other shadowmaster enclaves around the Realms to give orders, check on the members, and provide inspiration as needed. She may be sent to a city to establish a new guild presence or to eliminate a branch of the guild that is deviating from what the Shadowmasters in Telflamm have decreed. She wields her authority as a shadowlord with a ruthless hand since she really does not care about the members of the guild as individuals. She was never shown any kind of pity, so she never learned to show any. She maintains her position with the merchant as well, who enjoys a more lucrative trade thanks to his new connection with the Shadowmasters (and his compliance with their will).

Riggilla stands 5 feet 2 inches tall and weighs a scant 120 lbs. Her dusky skin she attributes to her meld with the shadows, though her slightly pointed ears give away her elven heritage. She has silvery hair that she keeps cut short and dyed black. She is lithe and athletic -- a product of her strenuous upbringing. She wears a suit of mithral armor that is blackened. It was a "present" from a former associate in the Shadowmasters who met his fate at her hands. Her facial features are harsh and somewhat masculine, and she easily passes for a male most of the time.

Because of her past, Riggilla hates dwarves with a passion and elves almost as much. With humans she feels most comfortable, though she does not mind gnomes and halflings. With her shadow-born powers, she likes to inspire fear in others and will use her hat of disguise and shadow abilities to seem to appear from the darkness like a wraith or a vampire. She usually gets the jump on her opponent, and she prefers a strike-and-retreat method of combat that maximizes her abilities and minimizes her vulnerabilities. Riggilla frequently takes advantage of the fact that she can see in magical darkness and most of her victims cannot. She is now a master thief because of her shadow-born abilities and lives in a wealthy but subdued lifestyle that suits her very well. She feels some sense of security with her position in the Shadowmasters and can afford whatever she wishes (with a little effort). She keeps her childhood as far in her past as possible.