From the back cover:
Evil takes many forms in the lands of Faerun. This book brings all of them out of the darkness and into the light.
These are the characters who have tested the mettle of the foremost heroes of the Forgotten Realms campaign world. They spread chaos and death wherever they venture, ruining what ever they touch. And they are coming to your campaign.
Inside this companion volume to Heroes' Lorebook you'll find complete game statistics and descriptions for a host of dastardly rogues, most of whom have never been described in a game accessory before.