Erode Defenses

Transmutation
Level: Artificer * 3, Magus * 2, Sorcerer */Wizard * 3, Warlock * 3
Components: V, S
Casting Time: 1 Standard Action
Range: close (25 ft. + 5 ft./2 levels)
Target: one creature
Duration: 1 round/level
Saving Throw: Fortitude negates (see below)
Spell Resistance: yes
  Your spell slowly begins to eat away at the defenses of your target. If the target fails its saving throw, it loses 1 point from any Damage Reduction and Natural Armor Bonus it may have. If the initial save was not successful, the target may attempt a new saving throw each round for the duration of the spell or continue to suffer cumulative losses. If the first save fails but a subsequent save succeeds, the eroding effects stop at that point, though any of the penalties already accrued remain until the spell expires. At the end of the spell's duration, the target's Damage Reduction and Natural Armor Bonus immediately return to normal. Only one erode defenses spell can affect a particular target at any one time.