By SR4 rules, a Bound Spirit can help a mage cast a spell, with the Aid Sorcery service.
Any summoned Spirit of Man with the Innate Spell power can cast a spell, generally as ordered to do so by its summoner.
Can my shaman task his Spirit of Man with the Innate Spell: Invisibility power, with making the shaman invisible, while tasking a bound Air Spirit with using Aid Sorcery to boost the Spirit of Man's spellcasting DP?

Assuming both spirits have the same Force, the total DP is 3xForce.

At high enough Force, that could exceed the mage's spellcasting DP.

sure, why not?
can't mages do something like that too?

I would not allow one Spirit to use Aid Sorcery on another Spirit.

SR4, p. 178, under Magical Services says the spirit can Aid its summoner with the various services. Not another spirit, even one summoned by the same magician.

Cool idea, though.

Peter

SR4, p. 178, under Loaned Services also says the spirit can aid any character with its services, if the summoner so chooses.

Good point, vollmond. I wish I had read the -whole- page.

So I guess it would be possible for one spirit to aid another's spellcasting. And summoning a spellcasting spirit of Force higher than one's own Magic attribute then would indeed allow casting of a spell at higher Force/effect than one could by himself (even with the added dice form the Aiding spirit).

Hmmm.... is there a chain reaction possible here somehow? I don't see it, but just wondering.

Peter

I don't see anything in the RAW about limiting how many spirits can use Aid Sorcery on a single target. Conceivably one could overcast and bind 5 of the appropriate spirit (assuming enough Charisma) and have a dice pool of amazingly high levels for that Invisibility... Force-12 spirits would give you 72 dice. Wow.

Note to OP, I don't think you would be able to swing it with 2 different types of spirit - they all have to be the Illusion type for your tradition (for Invisibility, anyway).

(edited for clarity)

Well, the OP was about a spirit casting the spell, which means a spirit of Man which can be given any spell the summoner knows. That spell could then be Aided by a spirit of the type associated with the spell type according to the summoners Tradition. (Not necessarily a spirit of Man.)

I believe there is a generic rule somewhere that limits the addition of dice to a Test from a particular class of source to one example of that class. So for Aid, only one spirit could add dice to the Test. For Foci, only one Focus could add to the Test. I don;t know where that rule is. Help anyone?

Peter