Neverwinter Nights 2 Feats Database: Feat Details
Death's Ruin
Feat ID: 2129
Type of Feat: General
Use: Automatic
Prerequisite: Granted by item only
Installation: Mask of the Betrayer

You can make sneak attacks and critical hits against undead creatures. However, you inflict only one-half your normal sneak attack damage (rounded down) when determining bonus damage for such attacks.