Spell Ablation: A defense against magical effects. Anything that ignores SR also ignores Spell Ablation (SA). Rather than sometimes completely negating spell effects like SR, SA reduces its effects, not entirely dissimilar to the difference between AC and DR. Whenever a creature with SA would be affected by a spell with any level-dependent variables as part of its effect, the spell's effective caster level is reduced by the creature's SA when determining those effects. The spell is not negated if this would reduce the effective caster level to less than the normal minimum required to cast the spell. However, if this would reduce the spell's effective caster level to less than 0, the spell is negated as though it had failed to bypass the creature's SR.
Range, area, number of targets, HD of creatures affected, and other factors that determine which creatures are affected are not influenced by SA, only the actual potency of the effect applied to those that are. Duration is affected only for spells that apply their effects individually to each of their subjects (or to their sole subject, in the case of single-target spells).
If a spell would affect multiple creatures, one or more of whom have SA, determine the effects of SA's caster level reduction for each creature independently.
If a creature has both SR and SA, the reduction in effective caster level does not apply to the caster level check to bypass SR. The two magical defenses apply independently of each other.
Multiple sources of SA do not stack. Use only the highest one.
A creature with SA who willingly accepts a spell can choose not to apply SA to that spell.
... not sure how to word how Spell Ablation affects powers. Something to do with reducing the effective amount of augmentation, but how, exactly? Probably capping it at the newly reduced effective manifester level and determining the effects accordingly, or something like that.