(Spheres of power) Mana siphon and vancian casters.

[fearcypher]

In a game I am running I have a mixed world of spheres of power and vancian casting.

I have a bounty hunter coming after the party with the mana siphon talent.

relevant text:

Your destructive blast saps the magic energy from your target, funneling it to you. A mana drain blast does nonlethal damage using d4 dice instead of d6 and your target must make a Fortitude save or lose 1 spell point. This loss increases by one die size (1d2, 1d3, 1d4, 1d6, etc.) for every five caster levels. You gain an equal number of temporary spell points that last for one round per caster level, though you cannot receive more spell points than your target loses. These temporary spell points do not stack with spell points from other targets, other instances of this ability, or any other source and expire after 1 round per caster level.

However the entire party are vancian casters. So I was wondering how to run it against them so that it still effects them.

I was thinking of running it as spellcrash except with no spell level limit(not that it matters in this case) and the casters losing one spell per spell point lost, and the spherecaster gaining one spellpoint per spell lost.

Is this a balanced way of running this effect?
Does anyone know a way it could be done better?

[GM Rednal]

Your intended way of running it seems fine. Frankly, it's not likely to matter too much in the long run - they lose spell slots and the bounty hunter gains spell points is about as complex as it needs to be. XD Definitely let the player choose which slots are lost, though. That's the normal rule and should be followed.

[Grovestrider]

I agree that the target of the mana siphon blast should be allowed to choose which slot is lost. I personally would also allow the target to choose to lose spell slots from any spell level (I wouldn't force them to lose their highest level spell slots first).