spell effect-you conjure a large ball of slime & throw it at the target
requisites-creoaquam(terran)25
range-throwing distance
duration-inst
target-ind.
tell me what you think of this spell.
What does it do when it hits, Abe? It's a ball of goo... so? That's the cause- what's the effect?
the ball of goo has 2 effects-it nausiates the target & it make him/her VERY slipery!
One would be PeCo (physical illness), the other maybe CrAq, so doing both together would add 2 magnitudes for Requisites. (Heh, unless you want to argue that "snot" is Corpus.)
Ars Magica spells aren't like certain other games where something just does "stuff" - it has to fit into the Forms, and most stuff can easily. But not everything. Creative idea, but might be hard to achieve (at low-medium levels) in Ars.
I was thinking corpus...but not snot
Ew... a death worse than fate! 
or in other words "It'snot Corpus" 
how about the bass effect be 55 instead of 25?
Then you need a reeeeeeeallllly big Kleenex with lots of soak! 
Ouch!
Puts a whole new meaning to a desperate mage "shooting his wad" at an enemy.
No no, then it becomes a Ritual, and a Ritual ball of goo is just ridiculous.
I don't know but I think you could use Herbam to create a sort of plant based goo. It should not be to hard to do. It would be nice and green and while it would not nauseate the target automatically, it might be disgusting and do it quite natrual and the person would be slippery.
I would however imagine that such a spell might be more a prank spell that an Apprentice might create to play a joke on his friends than something an adult and serious Magus would use his time creating.
Actually, creating a large, slippery area that creates treacherous footing is quite useful, and one of my own favorite cheap effects. Whether a CrHe (Carpet of River Moss) or CrAq (Black Ice, or Oiled Dancefloor) or whatever, an effect that reduces traction in an area can be devastating in the right circumstances.
thank you!