Staffs are very popular for talismans due to their material bonuses, but staffs are not the best weapons for a magi who know how to handle such implements of war.
If a Mu/He spell is used to change the staff into another weapon by letting it grow blades to become an axe or changing the whole thing into a sword, would it still be a staff for the purposes of the attuned bonuses of the talisman? The muto spell does not change the nature of the staff, just temporarily changes it into a axe or a sword or something else.
In my saga, if you used a muto spell to change a talisman staff into a sword you would not able use the shape and material bonuses for the staff while it was a sword... just as you cannot use your hands while you have used a muto spell to become a wolf. Shape and material bonuses are drawn from the symapthetic magical relationships of those shapes and materials. If something doesn't have that shape or isn't made of those materials, it no longer gains those bonuses.
Now, a canny magus could still get around this. An ax, which has a shaft of wood, would still gain the "staff" and "wood" bonuses because the shape and material are still there. Further, a sword with a miniature inlayed staff, or even a grip that was a wooden wand, would still gain those bonuses.
You could also do things which would improve to weapon as a Staff. For example the sprouting the thorns, being as hard as Iron etc. Yes this would need LOTS of penetration. But this is your talisman. I would say they actually have a lot of effect. I would say the first would add +4 damage to the weapon damage. I would say the transformation to weapon would make the weapon equivilent to a cudgel.
So with the 2 effects in play (One level 5 at personal and one level 10 at personal, sun, no size and no extra times per day). This turns the staff from
init +2 attack +3 dfn +3 dam +2
init +1 attack +4 dfn +1 dam +11
I would also add in something which makes it lighter to weild.....
If it penetrates, it works like a much nastier weapon. Still ultimately a staff, just with a lot more heft (and the need for a +1 strength not a -1).
I would say the bonuses remain staff bonuses, not other weapon bonuses. I based this on what we fundamentally understand about Muto: that the object is only superficially changed and that it is still its old self at the same time. For example, a human changed into a cat is still affected by Corpus even though there is apparently no Corpus material present. I feel the same should be true of the staff. Meanwhile I think the attunement/lab bonuses are based on fundamental nature, so you can see how that fits with the earlier comments.
Nothing about Muto says a change is superficial, but I can see that line of reasoning. An item has an Essential Nature, Muto doesn't change that at all. It changes the look, but I think it's deeper than superficial. For the period of the spell it is whatever it was transformed into. When the spell expires the Essential Nature expresses itself and it reverts to the true form. As far as your human example, I'd say that the Limit of the Soul is what protects a person changed into an animal from having animal spells work on him. The soul can't be destroyed/affected by Hermetic Magic.
Edit: I know it's a bit of handwaving, and I'm fine with that.
I meant it in the sense of not changing essential nature, the fundamental core of the thing.
This isn't right at all. The transformed human can be affected by Animal magic. My point was that, even with no Corpus parts at all remaining, the transformed person can still be affected by Corpus. I'm pretty sure RAW says this is due to essential nature, not the soul, which is why it is not the same for Bjornaer.
Our Saga rules invissible objects don't have a visible shape and therefore don't provide a shape bonus. This doesn't change the bonus, just negates it. I would say it can't change the essential nature of a thing as this is where the magic comes from.
So you can change an item out of shape or material, but would would temporarily loose the bonus. However a Bone wand becoming a bone dagger would still be bone and a Bone wand becoming and Iron wand would still be a wand. It would not gain a bonus for being either Iron or a dagger as the attunement process can only work off the essential nature of a thing. However it could gain mundane advantages from the shape or material
I know it's not exactly what you're asking, but have you considered a spear - even a staff that grows a blade to become a spear?
This I would probably allow to retain the bonii from being a staff, especially as most of the (magical) advantages of the staff appears to be from using it to point as something, and for that purpose, a speartip only strengthes the image, IMAO.
Sure, it would be a better weapon than a staff, but if the talisman retains it's attuned shape bonii while changed into another shape it has far more uses than just improving the weapon stats of a talisman staff. Change the staff into a ring or other piece of jewelry and you can bring your talisman where a weapon would bring unwanted attention and still get your +4 bonus to destroy things at a distance (or any other bonii you have attuned to the talisman).
Really, I'd disallow it. The bonus comes from the SHAPE. If it hasn't the appropriate shape, there's a disconnection between what it is supposed to be (a staff) and what it is (a ring). You've attuned the shape of a staff, yet it's no longer a staff => Your connection to the platonic form of the staff (which is what allows the shape bonuses) is broken.
In short, this seems too much like a cheap trick to me.
OTOH, allowing it to change shape while not keeping the bonus, sure! That way, you can sneak your talisman staff into that castle.
My original thought was more in the line of just letting the staff grow some blades and count as a poleaxe in combat while still being a staff for the purposes of throwing around some fireballs and whatnot. But if A can be B and still count as A, it might also be C while counting as A.
Turning a staff into a ring is far from what I originally imagined.
Revisiting, since I did such a horrid job the first time.
The change is not superficial. It is whatever it is changed into for the period of the spell. At the expiration of the spell it reverts to its Essential Nature. Bonuses would derive from whatever the current form is (wow, this opens anothr can of worms).
Your example of a human changed into an animal, by a MuCo(An) spell, gets into a sticky grey area. It is expressly stated in the description of Animal that the form of Animal cannot affect people. I attirbute that to the Limit of the Soul. Why would a MuCo spell continue to affect a person changed into an animal? Again, I'd say it's attributal to the Limit of the Soul. Animal spells don't work, even though the shape is correct, because of the soul. Why Co spells continue to work, I'll also attribute to the Limit of the Soul. He is a person, person has a form made in the image of God and he has a soul. Co spells reference that image, which resides as part of the soul. Note, it's referencing, not affecting. That's how I rationalize it. And again, I may be handwaving, but I think it's rational, and the inconsistentcy I can attribute to a game mechanic that is acceptable to the mythic paradigm. And it makes all the more sense (to me), when one considers that Corpus cannot affect inanimate human shapes, such as statues, which is puzzling to Hermetic theoriests, as per the description of Corpus. This must mean giants have a soul, because they can be affected by corpus, if the spell is designed with the appropriate size in mind.
Isn't that what I said above was what I meant by superficial?
I'm sorry, but this is very incorrect. First, it is explicitly stated that Animal spells do work on a human who has been Muto'd into an animal. They don't work on a human in human form. Second, it being due to the soul as opposed to essential nature would imply that Bjornaer must not have souls. (Having soul -> affected by Corpus as animal, necessarily implies not affected by Corpus -> not having a soul.) Rather, I'm pretty sure it's stated that the Bjornaer have two essential natures or two parts to their essential nature and that that is why they are not affected by Corpus when in Heartbeast form.
You've said this. Twice now. But you haven't cited anything, so I'm not relenting my position. I have attributed my understanding to the descriptions of the Forms in the MRB. I may be incorrect, I don't deny that. However, telling me that what I am saying is very wrong, without something to back it up (your status notwithstanding), doesn't make me inclined to accede your point of view.
But that's far more broken, isn't it? If the bonus comes from the shape (current) instead of the shape (essential nature), and you have an item that can change shape, then it should be aligned with the new shape's bonuses. Thus you could change its shape and attune some other bonus from its new shape. Just have it change shape to provide the bonus you want for the situation at hand. If you do the same for material it means any talisman can provide any attunement you want, as long as you are good enough at Muto, you just need to adjust it to the situation. That seems far more broken to me.
I prefer to have the bonus come from essential nature, not current state. To magic, Muto changes are superficial, not changing what the underlying thing really is. We could say Muto changes are sensed by magic akin to how MuIm changes are sensed by persons. So no matter what the staff may seem to be, it's still a staff underneath.
I can see saying there is a disconnect from the platonic form, but no that the bonus comes from shape itself, but I think saying "SHAPE" isn't a very good way to designate the origin.