Source: Races of Faerûn
Your ancestors long battled the insidious influence of shadow magic, and some of their descendants (including you) have a greater resistance to its effects.
Prerequisite: Talfir or Tethyrian human of any region
Region: The Western Heartlands.
Benefit: You get a +2 bonus on all saving throws against spells and spell-like abilities with the shadow descriptor. You also get a +2 bonus on all saving throws against spells and spell-like abilities that draw on the magic of the Shadow Weave. These benefits stack with each other.