Assay Resistance

(Complete Arcane, DnD 3.5)

Divination

Level: ; Cleric 4; Sorcerer/Wizard 4
Components: V, S
Casting Time: 1 swift action
Range: Personal
Target: You
Duration: 1 round/level

This spell enables you to divine the exact nature and vulnerabilities of a single creature's magical defenses, giving you a +10 bonus on caster level checks to overcome its spell resistance.
Assay resistance is effective only against one specific creature per casting, and you must be able to see the creature when you cast the spell.