FABRICATION OF MAGIC ITEMS
It is an obvious premise of the game that magic items are made somewhere by someone or something. A properly run campaign will be relatively stringent with respect to the number of available magic items, so your players will sooner or later express a desire to manufacture their own. Do not tell them how this is to be accomplished! In order to find out, they must consult with a sage (q.v.) or a high level character of the proper profession, the latter being detailed a bit hereafter.
Magic items are made by high level magic-users, except those items which are restricted to clerics and special racial items and books, artifacts and relics. Books (including tomes, librams and manuals), artifacts, and relics are of ancient manufacture, possibly from superior human or demi-human technology, perhaps of divine origin, thus books, artifacts, and relics cannot be made by players and come only from the Dungeon Master.
Dwarven and elven manufactured items—the +3 dwarven war hammer, certain other magic axes and hammers, cloaks and boots of elvenkind, magic arrows, magic bows in some cases, and even some magic daggers and swords—are likewise beyond the ken of player characters of these races. Only very old, very intelligent and wise dwarves and elves who have attained maximum level advancement are able to properly forge, fashion, and/or make these items and have the appropriate magicks and spells to change them into special items—ie. these items are likewise the precinct of the DM exclusively.