Spellfire deserves love. [3.5, Spellfire, PEACH]

[Amechra]

Raw Arcane Might [General]
Your every action is filled with a might that could only come from deep arcane forces.
Prerequisites: Constitution 13, Spellfire Wielder
Benefit: For the purposes of prerequisites you are capable of casting arcane spells of a level equal to either your Constitution modifier or one-half your character level (minimum 1), to a minimum of 0, whatever is lower.

Spell Eater [General]
You ache with a thirst for arcane magic. It makes sure you get what you want, at least...
Prerequisites: Constitution 13, Spellfire Wielder, Mage Slayer
Benefit: Whenever a spellcaster that you are threatening fails to cast a spell, you absorb a number of spell levels equal to the spell level of the spell that failed.
Special: Upon taking this feat, you gain a permanent -4 penalty to your caster level. This stacks with the penalty from Mage Slayer and any feat that has it as a prerequisite.

[peacenlove]

Raw Arcane Might [General]
Your every action is filled with a might that could only come from deep arcane forces.
Prerequisites: Constitution 13, Spellfire Wielder
Benefit: For the purposes of prerequisites you are capable of casting arcane spells of a level equal to either your Constitution modifier or one-half your character level (minimum 1), to a minimum of 0.

Whichever is greater or less? Also the sentence "minimum 0" is confusing since you already set a minimum at character level.

Also have you a homebrewed version of spellfire? Because the RAW one has some troubles (Absorption as standard or free action? Static reflex save. Supernatural ability but not really. Badly scaling healing power.) and needs to be rewritten even for clarity's sake.

[Amechra]

You see no editing to put something that was totally there when I first wrote this page back in!

I personally use this Spellfire revision.