illusion shadow 

Traditions arcane, occult

Cast [R] verbal; Trigger A spell or magical effect deals damage.

Range 60 feet; Targets the triggering spell

Exchanging material energy with that of the Shadow Plane, you transform the triggering spell into a partially illusory version of itself. Attempt to counteract the target spell. If the attempt is successful, any creatures that would be damaged by the spell instead take only half as much damage. but the spell otherwise works as normal. Treat shadow siphon's counteract level as 2 higher for this attempt.

Core Rulebook, page 368.