There is a CharacterSetHitpointsPercentage call. CharacterSetHitpointsPercentage(badGuy,50); halves badGuy's HP e.g. So if you could incorporate that into the spell somehow, I've not tried anything like that so I'm not sure how.
I've considered that but setting the health to an absolute percentage seems kind of tricky when i need to inflict, say 5% of the casters health as damage.
Entirely possible that i do not properly understand this though
