Powercast (3.5e Feat)
From D&D Wiki
Benefit: You can channel extra power into your spells. Your caster level is considered to be two levels higher when determining level-dependent parameters such as range, damage, and the ability to penetrate Spell Resistance. Alternatively, if you are multi-classed, you can use your normal caster level and add half of the difference between this and your overall character level (rounding down) before applying the +2 bonus. For instance, if you're a spellcaster with 3 levels of rogue and 4 levels of fighter (7 non-caster levels), your caster level increases by 7/2 + 2 = 5. Similarly, paladins and rangers (who normally cast at half their actual level) add half of their "missing" caster levels, and character races with racial hit dice and/or a level adjust may count these as non-caster levels. If you also have the Practiced Spellcaster feat, apply Practiced Spellcaster first, and reduce your remaining non-caster levels accordingly before applying Powercast: thus, the rogue/fighter in the previous example would count as having 3 non-caster levels rather than 7.