Penetrating Damage (metamagic feat)

[Anubis]

It does not overcome immunity to forms of energy, such as granted by Protection from Elements. Last sentence of the benefit description.

The basic idea is that this feat is to energy resistance as sure striking is to damage resistance. Maybe I should rename it "sure damaging?"

I took sure-striking as giving a +4 increase to a weapon's plus, for purposes of overcoming damage resistance ONLY. The cost of sure striking is +1.

I based the effect of the +1 to spell level by seeing what the real damage increase would be by increasing the spell level by +4, but with the extra damage applying to energy resistance only.

A double empowered Fireball was my base spell. It deals an extra 35 points of damage, or 17.5 extra if the critter saves. If the critter fails the save on a 3 or less, this averages at least +20 damage.

So the +1 spell level "sure damaging" effectively does an extra 20 points of damage for the purpose of overcoming energy resistance.

Since energy substition: sonic evades most energy resistances/immunities without increasing the spell level at all, I can't see this feat as unbalanced. It doesn't help against immune creatures, and it is hindered by unusually high resistances.

I'm willing to consider the feat overcoming only 10 points of energy resistance, but I'm curious what the reasoning would be behind that decision.

All very good points. Considering the limited use of this feat, I think it is probably balanced. I would make it a feat that has to be taken repeatedly for the effects to stack, however, other wise this would get messy when combined with Enhance Spell, Empower Spell, and Improved Metamagic.

 

[Al]

Bypassing 10 per +1 spell level is not nearly enough.

The reason is simple: at this level, you're better off simply using standard damage buffing spells.

For example, taking an Empowered Fireball and a Double Penetrating Damage Fireball.

The Empowered Fireball does 52.5 damage (caster level 10)
The Double Penetrating Damage Fireball does 35 damage, and penetrates 20 damage.

Thus, against a foe with 20 Fire Res or more, the Double Penetrating Damage Fireball does 2.5hps damage more than the Empowered Fireball (that's it). In exchange, the Empowered Fireball does 17.5 points more damage against non-Fire Res foes. For those with an intermediate amount, the comparison varies, but it is clear that Double Penetrating only begins to be useful if the opponent has Fire Res 18 or more.

Bearing in mind the cheapness of Elemental Substitution, and bearing in mind a comparison with straight damage-buffing, it seems clear (to my mind) that Penetrating Damage should bypass 20 as a fair boost. Otherwise, it is rarely worth memorising (as even against Fire Res creatures, the damage increment is trivial).