This is a spell that I'm currently working on, however I found I had very little to base it on in order to determine the spell level. I wasn't able to find something similar enough, so I'm unsure of where to set it, and hoping for opinions:
I’ana’s High Reversal
School: Evocation
Level: Bard X, Sorcerer/Wizard X, Witch XCasting
Casting Time: 1 Standard action
Components: V, S, MEffect
Target: one creature
Range: 25 ft. plus 5 ft./2 caster levels
Duration: instantaneous.
Saving Throw: none; Spell Resistance: yes.This spell fires a blast of energy at a single creature as a ranged touch attack. The blast glows in a range of colour from bright blue to bright purple depending on how injured the caster is (pure blue for entirely uninjured, purple increases as injury increases).
A creature hit by the blast takes 1d6 damage plus additional damage depending on how much the caster is injured.
To determine extra damage dealt, divide the caster’s maximum hp by their number of hd, and round up to the nearest whole number. This spell deals an additional 1d6 damage for each full amount of this result that is missing at the time of casting, to a maximum of 1d6 extra damage per 2 caster levels.
For example: A caster with 10hd, 100 max hp, and 50 current hp casts this spell. 100hp/10hd = 10hp, so this spell deals 1d6 additional damage for every 10 hp the caster is missing. Since the caster is missing 50 hp, this spell will deal 1d6 + 5d6 damage.
Agreed with GeneticDrift on all points. Looks like a level 2 spell for bard/sorc/wiz, 3 for witch.
@GeneticDrift: Would you cap it at 1d6+10d6 or at a flat 10d6 (i.e. 1d6+9d6)?
Page 128, Ultimate Magic indicates a second level spell with a single target should deal a maximum of 10 dice of damage.
Since there is no saving throw allowed, that might be worth a one level bump.
I like the 'when caster is damaged the spell does more damage' but I'd like to think there is an easier way to implement it.