The spell is an attempt to give more freedom to the player and allow for better RP without giving OP tools or weapons. It is directed toward high fantasy settings with very common magic.
The idea being that a player can make his own costume items mostly during downtime. Such Items are not tools or weapons or magical. And I tried to balance the spell with the possibility of failure.
Artistic muse – 1st level transmutation
Casting Time: concentration, several hours
Components: V, S, M (varies)
A work of art is created from non magical raw materials with dimensions depending on the raw materials but no larger than 2m^3. The caster rolls a spellcasting ability check for each iteration of the spell (lasting 1 hour). The DC is (12 + number of past checks ever done on that object). Failure leads to the loss of the art and all materials. Success adds 2 tenths of the materials value and allows the caster to add, remove or change details to the art. The caster can end the magic safely only after the current hour of work is done. The caster must be completely undisturbed during casting and can't make any action at all until the spell ends. He automatically fails all save rolls and his passive perception drops to 0 during casting. The art is non magical and the number of hours required to create it are for the DM to decide as well whether to tell the player the exact number of hours or just give him a general idea (size, complexity and monetary value are the parameters). If the magic is stopped by the caster it can be resumed (DC will include all past work on the item by all casters). Only one caster may work on an item at a given time. No weapons, armor, tools or buildings could be made with the spell as it creates fairly weak items. Each level above 1st adds an additional tenth to the materials value per iteration.
Classes: bard, sorcerer, wizard, cleric
The size limitation is put to limit the items to things that could be worn or put on display and not require structural integrity.
The raw materials must be gathered by the caster beforehand in order for the spell to allow customization without breaking economies.
I've done some math the maximum a player can use this for gold is about the same as wish and only on the higher levels so I think it is balanced in that regard but I might have overlooked something.
the helplessness of the caster during casting is in order to not allow a player to change his gear during play to skip over.
I've given the DM control on the difficulty level of each item with determining how many hours are required to finish an item (basically the ability to refuse absurdities) and set it so the player can work on an item over a long time. An example of such absurdity would be a character with low Intelligence that wants to make an automaton with gears and such. Its not a tool or a weapon or armor and it can fit the size and description but it would make little sense so the DM would set the number of hours required to finish the art high thus giving lower chances of success. The player however would still have a chance to complete a very difficult task over a long time and the DM might reduce the hours needed after several failed attempts as the character learned from past mistakes.
I'd like to get criticism of how this spell could break a game because I covered anything I could think of and might (probably) have missed something.
I'd like remarks about my wording as I'm not the most coherent writer. Suggestion on improving the wording are welcome.