Not much is known about the Black Widow.
 
A male dark elf, Nezznar had managed to bring the Cragmaws and the Redbrands under his fist for the sole purpose of preventing the English from discovering Wave Echo Cave. It is possible this is because he was in the process of plundering its wealth, as he still had obstacles in the way.
 
In particular, he managed to use this to trick the party into a compromising situation. The party ultimately prevailed and Nezznar is now dead.