Prime_Evil said:
I think one reason that fantasy authors have been cautious about the magical creation of matter ex nihilo is entirely pragmatic - it is a potential game-changer and thinking through all of the possible implications can be difficult.
The way I handle it in my Phalanos setting is that the matter is not
really created by the spell, it is only exchanged through a process
remotely similar to teleportation: When the sorcerer casts his Crea-
te Water to fill a waterskin, the air in the waterskin is transported to
"somewhere else" while the same volume of water from "somewhe-
re else" is transported into the waterskin. The "failure potential" of
the Create spells is the problem that the sorcerer cannot determine
where "somewhere else" is. For example, a spell failure during the
attempt to fill the waterskin of Character A could result in the wa-
ter coming from the full waterskin of Character B, which then con-
tains the air from Character A's waterskin. A spell failure during an
attempt to Create Gold could empty the purse of the merchant stan-
ding next to the sorcerer, who might wonder why his purse sudden-
ly becomes light while gold appeares in the hand of the caster ...