Hi
I'm on the brink of starting a sorcerer fantasy game set in a mythical middle ages German principality where the dark woods seem to be slowly creeping up on the little villages dotted across the landscape, monks are more likely to be drunk and mad than wise and pious and wildeyed nuns bury their unwanted infants in the herb garden.
The PCs are all the children of the village witch and can choose any age they like between twelve and early twenties. (I realize I'm herding them a bit on this point, but everyone liked the idea). I plan to make sorcery a folk loristic affair with eye of newt and feet of crows going in to the cauldron, while you chant arcane rhymes and burn hemlock harvested under the full moon. (The fumes might give you a nice, drugrelated bonus too ;))

I have quite a few ideas for this game and setting which I would appreciate some thoughts on - you need not have an opinion on all of it to reply - so here goes:

1) I consider giving demons an extra feature, namely some personalized weakness in tune with folklore where most supernatural beings have something of the sort. It could be anything; fear of crucifixes, being momentarily immobilized if salt is thrown into its face, shying away from briers, needing to be carried across running water (only passers or possessors, and possibly parasites transferred to host; could get rather amusing particularly if the player doesn't know about it from onset). With a wide range of possibilities it shouldn't become too much of an obstacle as it's hard to know just what weakness a particular demon has.
But is this still a bad idea? If yes, why? If no, should the PCs know what their demon's weakness is? Clearly this would be a closely guarded secret.

2) In actual European lore on witchcraft there's a marked fear of sorcerers misusing and perverting the power of holy items such as the wafer or the alterwine in their rituals. But I'm wondering if it would be wiser to ignore this as I don't want the game to be centered on religious issues and don't plan to let Christianity have any "real" cosmic importance with angels and such?

3) Sorcery is a dark and mysterious thing and it is very hard to "design" a demon; a sorcerer will have general idea of what he or she is trying to conjure up, but it requires a high lore and a very good roll upon contacting to get the details right.
Is this a good way to give sorcery a certain feel, or is it just annoying? The players will of course be allowed to design their starting demon. (Except if someone wants some power twenty horror; Mum knows better and will not have allowed it. I don't expect this to be a problem however, as my group so far has been anxious about anything too big to control).

4) All the witch's children - except whoever chooses to have the oldest PC - are fathered by her demon lover (bound to some other sorcerer somewhere else) who comes by the village occasionally. I'm thinking about giving them a younger NPC sibling, who's going to be the only demon child of the bunch, who thinks it's all unfair and who desperately wants to be human. It'll be bound to its mother - for whom I plan a horrible death pretty early on so the PCs can be on their own - and have some need it can fulfill itself, because the players will think it is human (they don't know the man who visits their mother is really a demon) and it will pretend to be.
Is it unfair of me to fit them out with this extra NPC demon they haven't asked for and won't really have control over? It's going to be a lot more tough and ruthless than your average ten year old child, but it's also going to be more "human" than most demons: It cares about its siblings - even though it is also very jealous of them because they're human - and it will generally have the same feelings and desires that human beings have.

~May

May wrote: I'm on the brink of starting a sorcerer fantasy game set in a mythical middle ages German principality

1) I consider giving demons an extra feature, namely some personalized weakness in tune with folklore where most supernatural beings have something of the sort... But is this still a bad idea? If yes, why? If no, should the PCs know what their demon's weakness is? Clearly this would be a closely guarded secret.

2) In actual European lore on witchcraft there's a marked fear of sorcerers misusing and perverting the power of holy items such as the wafer or the alterwine in their rituals. But I'm wondering if it would be wiser to ignore this as I don't want the game to be centered on religious issues and don't plan to let Christianity have any "real" cosmic importance with angels and such?

3) Sorcery is a dark and mysterious thing and it is very hard to "design" a demon; a sorcerer will have general idea of what he or she is trying to conjure up, but it requires a high lore and a very good roll upon contacting to get the details right.

I think James said everything I was going to say about 1-3.  I wanted to comment on:

May wrote:
4) All the witch's children - except whoever chooses to have the oldest PC - are fathered by her demon lover (bound to some other sorcerer somewhere else) who comes by the village occasionally. I'm thinking about giving them a younger NPC sibling, who's going to be the only demon child of the bunch, who thinks it's all unfair and who desperately wants to be human. It'll be bound to its mother - for whom I plan a horrible death pretty early on so the PCs can be on their own - and have some need it can fulfill itself, because the players will think it is human (they don't know the man who visits their mother is really a demon) and it will pretend to be.
Is it unfair of me to fit them out with this extra NPC demon they haven't asked for and won't really have control over? It's going to be a lot more tough and ruthless than your average ten year old child, but it's also going to be more "human" than most demons: It cares about its siblings - even though it is also very jealous of them because they're human - and it will generally have the same feelings and desires that human beings have.