Diminish Resistance

Transmutation
Level: Artificer * 2, Bard * 2, Cleric */Oracle * 2, Inquisitor * 2, Magus * 2, Sorcerer */Wizard * 2, Warlock * 2
Components: V, S, M/DF (a pinch of coarse sand)
Casting Time: 1 Standard Action
Range: medium (100 ft. + 10 ft./level)
Target: one creature
Duration: 1 round/level (D)
Saving Throw: Fortitude negates
Spell Resistance: yes
  You weaken a creature's resistance against one energy type you select: acid, cold, electricity, fire, or sonic. The creature's resistance to that energy type decreases by 5 (minimum 0), plus an additional 5 for every 5 Caster Levels beyond 3rd (to a maximum of 20 at 18th level).