Curse of Distraction

 
Prerequisite(s): Curse Ability, any other hexblade feat
 
Benefit: When you use your hexblade curse ability, your victim must make a concentration check vs DC 15 + Spell level in order to cast a spell. A greater hexblade curse increases the curse to 20 + Spell level, a Dire curse increases the DC to 25 + Spell level.
 
Source: Dragon Magazine #339