Felix: If I am pedantic on a matter such as this it is not because I am punishing my players, but because I'm pedantic about the stories that power my world. I want the logic of my world to be perfectly consistant, and I want to be able to attribrate a situation in which a PC wants to create an object by as consistant of a standard as possible.
By what standard is a ladder, a sack, a suit of clothes, or a Louisville slugger less a product of craft than a bowshaft? Lets take for example the extreme cases. One player wants to evoke this power to create a louisville slugger; the other wants to evoke this power to create some simple poison say hornet toxin. The first player announces his action, and I say 'Ok, great you've got a club'. The second player thinks "Well that was easy enough.", and announces his action. To his great surprise I start hedging around like I'm not going to let him do it. He glances back at the spell. I point to the part that says he needs a skill check to make complex items. He asks me quite reasonably, "Why did Joe not have to make a skill check in order to make a wooden club?"
How am I to answer?
1) Poison is more complex than wood. Errr... no. Wood is more complex than poison. With fluid poison you are probably dealing with a few simple 'molecules' (or whatever chemicals are made of in a fantasy setting) in an amorphous form. With wood you are dealing with a large number of complex molecules arranged in complex structures to give it the light weight, pliancy, resilancy, and strength that we expect when we think of 'Louisville Sluggers'.
2) You aren't as familiar with hornet toxin as Joe is with wood. Errr... no. Joe doesn't have any Craft (wood) skill. Joe and Bob have both been stung by hornets. More to the point, Joe doesn't know any more about the internal structure that makes wood wood than Bob does about the internal structure of poisons. Both just know what it looks like and what it does.
3) Hornet toxin is more valuable than wood. Err, so what? Basically, I'm making a meta-game appeal to the player - "Don't you see how broken this spell would be if I let you make valuable things with it?" Why should the spell care what is valuable? How does the spell 'know' what is valuable? Why is the spell/power debating value with the caster. Isn't value a pretty arbitrary standard? We usually think of silk as being more valuable than cotton, but that has not necessarily been true for all cultures everywhere in history. Try buying a natural linen garment today. It won't be inexpensive, even if it was in the middle ages. A polypropaleen garment is common today, but would have been invaluable 50 years ago. I just might be able to make an arguement stick that valuable things have some property that requires a higher skill check than common things, but if I make that arguement stick then I have the opinion I previously cited.
3) Hornet toxin is more useful than a club. Again, this is a meta-game arguement, not one based on the myth of my game. How does a spell know what is useful? Why is the spell/power debating utility with the character? Isn't utility a pretty arbitrary and subjective standard anyway? Clearly, joe thought a club would be more useful than hornet toxin. If you are at the bottom of a well, a ladder is more useful than a club. This agruement is so heavily influenced by the DM's rather petty desire to not have his plans disrupted, that I'd never even consider this an arguement.
It is actually rather reasonable that neither Bill nor Joe could adequately imagine the structure of the thing that they make, but if I did that I better rewrite the spell/power to one which suits the myth of my world. As it is written, it is a creation power - which I assumes means 'something out of nothing'. It is not a Divine power. If it was, I might make the arguement that you weren't really creating anything, you were stamping things out from a spiritual club shaped mold that defined 'clubs'. Perhaps I might argue then that commonality of an item defined its accessibility - sort of like looking through a database to find what you needed. But in that case, I wouldn't expect craft skill checks to have anything to do with it - and might require 'Knowledge - Planes' or some similarly esoteric lore. Or, if it was a summoning spell, I might argue that nothing was getting created, it was just getting temporarily moved from one place to another - but again, in this case craft skill checks should have nothing to do with the process. Besides, I'd have to worry about the PC's trying to use the spell to steal something temporarily from a nearby NPC on the assumption that the spell would try to grab some 'nearest' object, and I'd have to come up with a myth explaining non-intuitive 'nearness'. Or, if it was a transmutation type power - a sort of lesser polymorph any object - I might reasonably insist that the player provide a toothpick if he wishes to make a ladder, or a rag if he wants a sack, or a bit of grass if he wants a rope. But it is not that sort of power, and moreover such a spell/power while interesting doesn't necessarily explain why craft checks are needed in some cases and not in others.
So, what I think I could argue is that making a club requires a more common skill, and making a poison requires a less common skill. Moreover, I might argue that chemisty is a more difficult skill, requiring training - being less intuitive compared to shaping wood - and consequently the DC's are slightly higher. If a person wanted to envoke the power in question to make a club - I'd set a low DC like 5, and apply some sort of minor penalty to the quality of the club for each point of failure. The more complex the wooden object, the higher the DC. For instance, on a roll of 1 (no modifiers), I might drop the clubs h.p. by 4, and its hardness by 2, and its to hit by -1. You end up with a fragile, somewhat clumsy club. Most of the time, you need up with a club. If you are particularly good, you end up with a masterwork club. Same sort of thing applies to poison, just the DC's are 5 or so higher and the consequences of failure tend to be more dramatic (you get something that isn't poisonous, or at least isn't poisonous enough to quickly effect the target).
