Elemental Spellcasting [Fire]( Planar Handbook, p. 39)
Choose an element (air, earth, fi re, or water). You cast spells with that descriptor more effectively than normal.
Knowledge (the planes) 2 ranks,
You cast spells with the chosen descriptor at +1 caster level.
You can gain this feat multiple times. Its effects do not stack. Each time you take this feat, it applies to a new element.