Hlanta Melshimber
Hlanta Melshimber is the current matriarch of House Melshimber of Waterdeep. Considered one of the most dangerous social foes among the noble circles, Lady Hlanta Melshimber is a well-known woman whose ability to wield magic is far exceeded by her skills in manipulation and information gathering. Few ask her about her business, as that gives her an excuse to pry into theirs, so she often conducts clandestine business at her villa without interruption.
Every month, she has agents seeding the taverns, inns, and noble parties with carefully-planned rumors and stories about what she is up to, and waiting to see who takes the bait. One of her oldest and most-believed rumors involves her knowing how to brew a number of insidious poisons; the would-be assassins who sought her aid have often been uncovered by the watch soon after consulting her.
Currently, she toys with the affections of Duhlark Kolat the Transmuter; she arranged the Midsummer theft of a number of secrets from his tower. She has sold a number of his rare items, and she is also the source of many unique spells being sold to certain mages (through third and fourth parties, of course), once she masters them.