In standard AD&D magic, there are three outer components: verbal (talking), somatic (moving), and material (objects). There is a mental component also. If a fighter copies a mage’s words exactly, with exactly the same inflection, makes the exact same movements, and uses the exact same objects, the fighter will not produce the same results. There is something in the mage’s mind that transforms the outer components into magic.
There are three checks that balance the power of the spellcaster with the power of other characters: the caster must be able to speak; the caster must be able to move; and the caster must have specific objects. For some, more powerful, spells, the objects required are very rare and expensive. This limits the use of the more powerful spells.
There are also some advantages in AD&D style magic that do not always show up in other forms. The AD&D wizard can memorize spells without having to study them for long periods of time. A wizard can find a new spell and memorize it after only a few hours of rest.
When modifying how magic works, keep these in mind. If you change one of them, change something else to balance it out.
