Shadow Veil

 
Prerequisite(s): Ability to cast 2nd level spells.
 
Benefit: As long as you have a darkness spell of 2nd level or higher available to cast, you can obscure the vision of a subject within 30 feet as a standard action. If the subject fails a Will save, it treats all other creatures and objects as though they had concealment and takes a -5 penalty on Spot checks for 1 round. As a secondary benefit, you gain a +1 competence bonus to your caster level when casting darkness spells.
 
Source: Complete Mage