Metamagic House Rules
The following rules system is an alternate for the rules for Metamagic used in the Core Rule Book. They should be used in place of the existing rules that require spells use a higher level spell slot when Metamagic feats are utilized.
All Metamagic can be applied spontaneously by all casting classes. Each specific Metamagic feat would still have to be selected by the character as a feat in order to be used, just as in the existing rules. Each time a feat is selected, it allows the caster to use that feat to modify a spell a number of times per day equal to their Primary Casting Ability Score Modifier (Int mod for Wizards, Cha mod for Sorcerers, Wis mod for Clerics, etc). For casters with multiple casting classes, use the highest primary stat to determine how many times per day each feat could be used. Modifying a spell cast from any class that the character has available counts as one use of this feat.
First, spontaneously applying the Metamagic feat, whatever it is, requires a move action. This move action must occur in the same round that the spell is cast. The only exception to this is the Quicken Spell feat, which when utilized, only requires a free action to add In addition, whenever a spell is Quickened, adding additional Metamagic feats also only requires a free action. As with any casting, spellcasters can choose to Cast Defensively to avoid attacks of opportunity during the casting of a Metamagic-enhanced spell, in which case the Concentration check for casting defensively is DC 15 + 2x the adjusted level of the spell.
At the end of the casting, if the spell was not disrupted, the spellcaster needs to make a Spellcraft check at DC equal to 15 + adjusted level of the spell. So, a Maximized Fireball has an adjusted level of 6 (Fireball level 3 + 3 for Maximize), making the DC 21 (15 + 6). A Silent (+ 1), Still (+ 1), Maximized (+ 3), Empowered (+ 2) Fireball has an adjusted level of 10, so the DC is 25 (15 + 10).
Note that it is possible to use Metamagic to raise a spell beyond your character’s maximum spell level. So a 7th level Wizard, who can normally only cast spells up to 4th level, could still Maximize a Fireball, even though he cannot actually cast 6th level spells yet. It is just much more difficult to do so. If the adjusted level of a spell is higher than the highest level spell that the spellcaster can normally cast, and addition + 5 is added to the Spellcraft DC for each level over the spellcaster’s maximum spell level (+ 5 for one level, + 10 for the next level, and so on). So, our 7th level mage would add + 10 to his DC because his Maximized Fireball is two spell levels higher than the maximum spell level he can normally cast. So the DC for the 7th level caster would be 31 (15 + 6 + 10).
If the Spellcraft check at the end of the casting fails then you lose control of the energy that you are building into the spell. This causes the spell to fail, and you to take hit point damage equal to spell level from raw magic energy (no save and no resistance applies). So, in the above examples, a failure on the Maximized Fireball would take 6 points of damage, while the Silent, Still, Maximized, Empowered Fireball would result in 13 points of damage. If the Spellcraft check roll is a natural one, then the spell is Fumbled, and in addition to the damage taken for a failure the player pulls a card from the Fumble deck and applies the result. If the Spellcraft check roll is a natural twenty, then the spell is a Critical. The spell goes off and the caster can choose to either double the power of the spell or to retain the original spell in memory.