Suppose that in the course of an adventure, you come across some magic or otherwise special item (magic, or has special properties, or both); for instance, you find a necklace of resistance, or an animal with a hide that's immune to slash/pierce, or something of that nature.
Is it generally possible, either within the system itself or commonly in house rules, to allow characters to try to "repurpose" these items to craft weapons, armor or items that have special properties? Some mechanic that reduces the crafting cost, obviates the requirement to know a spell or have a feat, or makes it possible to create something not otherwise available. For instance, maybe you kill a medusa and tie its head on a stick… Or something.
I am very new to tabletop role playing, so forgive me if this is a silly question. I'm just thinking that, in "real" life, it seems like it could be possible to do this kind of thing, except, of course, no magic and not many special physical properties…
Best Answer
An item is allowed to have additional magics added to it, where the cost of the addition is the cost of the final product minus its current value. That is, take a +1 quarterstaff (2300 gp) and make it a +2 quarterstaff (8300 gp) for 6000 gp. See Creating Magic Items – Adding New Abilities:
For many items, combining functions (rather than upgrading them as with weapons) in one item carries a price premium equal in value to half the value of any functions after the first. This would also be part of the cost of adding magic to an already-magic item.
Stuff like directly using hides or medusa heads to make items, kind of. By default, yes, your character needs to have the appropriate materials (whose worth equals the crafting cost of the item), but what the “appropriate materials” are is left undefined and up to the DM.
Thus a DM may decide that a spike, gem, etc. is worth a certain amount towards the crafting cost of the item (e.g. that sword costs 2000 gp to make, but the gem you just found can be used for a part of it: you only need to provide materials [steel, leather, whatever] worth 1000 for the remainder of the sword). Most of the time, though, it’s more like “I go to the blacksmith and buy whatever I need for the sword from him.” Requiring specific, especially rare, materials doesn’t really occur in the rules except sometimes for certain spells (e.g. raise dead requires diamond dust).
I haven’t personally seen one, but I’d be surprised if no one’s drawn up lists of explicit materials for particular items. I doubt it’s official, though.