uncommon abjuration sorcerer 

Bloodline imperial

Cast [R] somatic; Trigger A creature within range that you can see Casts a Spell.

Range 120 feet; Targets the spell cast by the triggering creature

You undermine the target spell, making it easier to defend against. You reduce the spell's level by 1, and targets of the spell gain a +2 status bonus to any saving throws, skill checks, AC, or DC against it.

You can't reduce the spell's level below its minimum. For example, a 5th-level cone of cold would remain 5th-level, but a 5th-level fireball would become 4th-level. Targets still gain all the other benefits, even if you don't reduce the spell's level.

Core Rulebook, page 403.