I've been thinking about the age-old idea of the spellcaster's blood being used to empower their magic. It's a theme that's been prevalent in fantasy fiction for a long time, but I don't see any such options for a Pathfinder wizard.
I would like to get opinions on the balance, usefulness and such of this feat:
Blood Metamagic
Prerequisites:
* Iron Will
* Able to cast 2nd level spells (maybe arcane only?)
* Any metamagic feat
Benefit:
When casting a spell, you may use Blood Metamagic to apply one metamagic feat you know without increasing the level of the spell or the casting time. You immediately suffer a number of points of Constitution damage equal to the number of levels the metamagic feat would normally increase the spell by. Even though this feat does not modify the spell's actual level, you cannot use this feat to cast a spell whose modified spell level would be above the level of the highest-level spell that you are capable of casting. A spellcaster immune to Constitution damage cannot use this feat.
The 3.5 Book of Erotic Fantasy had a 3 level prestige class called the Metaphysical Spellshaper that had a similar ability.
Only that one allowed the character to take ability damage to any single (per metamagic feat to be applied) ability score equal to the spell level increase in return for spontaneously applying the metamagic feat.
The biggest advantage (and possibly a rather unbalanced one) is that it allows the character to improve the spell beyond what they'd normally be able to.
For instance, a 7th level spellcaster would be able to cast a maximized fireball using this class ability.
On the downside, the ability damage from the class ability can't be magically healed unless the healer succeeds on a DC 20 caster level check.
I'm not trying to go for power. I'm looking to create a nice useful ability that has a cost attached to it that will make the caster think twice before using it.
Maybe good for emergencies, which would fit the flavour nicely.
Is the cost too great? Too little? What would happen if we replaced the points of Con damage with 1d6 hp damage per metamagic level?
Perhaps HP damage instead of con would be a better idea.
1d4 or 1d6.
What you could do is apply the effects of a spell to yourself (I've been thinking about this for similar ideas and for cursed items).
My thinking is:
An inflict-line spell (or Cure, if you are undead, or similar if you are immune to either) of level equal to Spell level with a boost of:
+1 metamagic: +25% damage
+2 metamagic: Empower (+50%)
+3 metamagic: Maximize (~+100%)
Caster level and caster stat is your own. Any feats that boost spell penetration (if it applies) or spell DCs are not used.
So, I want to cast a maximized fireball. Fireball is 3rd level, maximize is +3.
I become the target of a maximized Inflict Serious Wounds, taking 24+caster level (max 15) damage unless I make my Will save against 13+(my caster stat), in which case I take half.
I think it's important that the 'backlash' scale by both the base spell and the effect you are shooting for.