I am triying to piece together a spell to give a magus bear-like big claws (+0 ini, +5 attack, +3 def, +4 damage).
I am thinking MuCo(An)10:
Base 2 (give a minor ability) + 2 duration (Sun) +1 size (magus is +2 size) + 1 not so minor (claws are quite big and impactful) + free requisite.
What do you think? Do you think that the “not so minor” extra is necesary? (Could be quite important for penetration purposes)
I would argue that you don't need the +1 for Big Claws unless you want to make sure the spell gives them Big Claws
By normal, I would assume that the spell gives Claws according to the size of the target [in this case, probably will give normal Claws for size +0 and lower, but big claws for +1 or higher]
You need to add + 1 Part, because you want your mage to remain mostly a mage, specifically able to be able to talk and keep casting. The spell is only transformation the nails to claws, thus Part.
Although the mage is size +2, the part you are affecting is not that big, so like @altidiya said the +1 for size is in this case superfluous. The spell would be affecting the whole body, that would be a different story.
To summarise:
Base 2 seems appropriate, +2 Sun, +1 Part, Pers, so a final MuCo(An) 5.
The ST might decide to give the mage a -2 to spell casting since his hand gesture is a bit more limited, but you could add a +1 to the spell for additional function and have retractile claws (this modifier is used with certain published spells that do a little bit more than the guideline).
Not necessarily. Just like Eyes of the Cat gives the target the cat's ability to see in the dark using T:Ind (because all of the target's eyes are affected), this spell can give claws with T:Ind, provided that all of the target's appendages grow such claws. So the claws would be grown on both both hands AND feet.
It would be T:Part only if he wanted a single appendage to grow claws.
Note that claws make some finer manipulations difficult, so the storyguide could reasonably say that the spell imposes a small penalty (I'd say -2) to fine hand movements -- such as spellcasting motions.
I'd say it's T:Ind because you are changing the magus (rather than just his nails) to give him (rather than just his nails) a minor ability: namely, to have a weapon always at hand - in fact, a very average weapon in terms of bonuses, nothing that deserves an extra magnitude. Of course, that's T:Ind +1 Size because the whole magus is size +2, so the final Level is the same as if it had been T:Part without size modifiers: Level 5.
Do consider reducing the spell Duration to Diameter - after all, few fights last longer than 20 rounds, and being stuck with big bear claws until the next dawn or dusk can bring a host of problems. Then again, you might want to go with retractile claws, a bit like Wolverine (the Marvel superhero) as Ezechiel3571 suggested. Personally, I'd still consider that nothing more than a minor ability, with no need for extra magnitudes.
One thing I'd adjust, however, are the stats of the claws. Having the claws of a bear does not really allow you to attack and defend as if a bear, with its strength and thick skin. I'd eyeball them as a dagger (0 Init, +2 Atk, 0 Def, +3 Dam), using Brawl as the combat ability; or maybe as a shortsword (1 Init, +3 Atk, +1 Def, +5 Dam) if they are really big (14+ inches, much bigger than a bear's) in which cased they'd be used with the Single Weapon Ability, rather than Brawl.
You are giving an ability to the whole Individual just like so many other MuCo(An) spells using the same guideline. It’s well established Part is not needed.
I like small claws as the baseline, and then add magnitudes for large claws.
I just want to say that it's been a long day and I initially read this thread title as "a spell to grow clams."
But I can see growing claws would perhaps make sense in a covenant's saga, too.
As you were...
Aren't clams vermin with a source of mud? ReAn the "Magus Clam Bake"!
Those are all really good comments. I reached to the diameter duration conclusion too.
I think that the magus should not be able to use gestures at all with claws (-5).
Then, the final count should be:
Base 2 (give a minor ability) + 1 duration (diameter) +1 size (magus is +2 size) + free requisite.
For a final count of 4 spell level. 5 if you consider small claws a baseline and big ones an improvement. You could compensate the bigger ability with the fact that you get the claws but also the inability to do gestures (as you would get being a Lion or Bear).