Fell Weaken

 
Prerequisite(s): Spellcaster.
 
Benefit: You can alter a spell that deals damage to foes so that any living creature that is dealt damage also takes a -4 penalty to Strength for 1 minute. Strength penalties from multiple spells enhanced by the Fell Weakening feat do not stack. A fell weakening spell uses up a spell slot one level higher than the spell's actual level.
 
 
Source: Libris Mortis: The Book of the Dead