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Here are some excerpts from an article in Dragon #200, “The Color of Magic” (pp. 28-31) by Dan Joyce.
1st: The article suggests customizing the standard spells for individual characters by making cosmetic changes but keeping the mechanics the same.
2nd: The article suggests that a mage can use ad hoc magic (without casting a spell) to do anything the mage could do by mundane means.
The existing D&D spells from the D&D Cyclopedia cover most magical effects already. New spells are often just minor variations of old ones. Bardolphs electromagnetic barrier sounds novel, but if it measures 20 x 60, prevents the passage of creatures with fewer than four hit dice, and does 1-6 points of damage to all others, then it’s not very different from a wall of fire or wall of ice. At least, it’s not very different in terms of game mechanics. In terms of game atmosphere (how the players perceive it), it could be very different indeed!
This is the key to creating hundreds of new spells to suit any kind of spell-caster: make cosmetic changes to existing spells. Describe spells differently. Magic missile need not be a shimmering arrow. It could be a telekinetic fist, a jet of flame, or a steel pin stuck into a voodoo doll. The game mechanics remain the same. All that changes is how these effects are brought about. Hence, a magic missile variant will still do 2-7 points of damage, with a range of 150' and a duration of one round. A shield spell still grants a saving throw. As for the rest, use your imagination. Maybe Maximus the Black casts magic missile by momentarily enchanting his dagger, then making a pass at a distant enemy with it. A cut, doing 2-7 points of damage, opens up on Maximus’ enemy, mirroring the swipe Maximus made with his dagger.
When you redefine how spells work, you may need to make some additional, minor changes for the sake of consistency. Maximus the Black, for instance, will always need a dagger or some other sharp implement with which to cast his version of magic missile. Such changes require careful thought from the DM and ought not to affect the overall power of the spell too greatly.
The benefit of this method is that there is no danger of upsetting the game balance. All the spell effects have been extensively playtested already. Redefining the causes just adds color, individuality, and panache.
Spells can also be styled so that they are in keeping with the overall conception of the character. As an example, take Illfrith the Ice Queen, a 5th-level magic-user NPC who lives in the DM’s “Northern Wastes” campaign. Ordinarily, she would not be able to use any ice magic until she reached 7th level (wall of ice). Yet she can cast fireball at 5th level. By describing her spells differently, however, she becomes a real Mistress of Ice Magic.
...later, in the same article...
The problem arises at the lower end of the magical scale. There are no spells less powerful than those of first level no cantrips, no minor prestidigitations. A Warlock may be able to fly and turn invisible, but he still has to cook his own breakfast. Xeno the Enchanter can conjure a fireball by waving his arms about, but he cannot light his pipe by snapping his fingers.
Magic-users need a bit more panache than this. In one sense they are only human even a Necromancer has to use the garderobe but they are also a breed apart. A magic-user who lowers himself to plebeian levels does a lot of harm to his image, and this illusion of power is one of his greatest assets. To maintain this image, the magic-user ought to be able to do ordinary things in an extraordinary way. Xeno should be able to light his pipe like that SNAP! He could probably poach his eggs without a campfire, too.
Don’t go overboard. A good rule of thumb is to allow magic-users to do magically only what they can already do by normal means. The idea is to enhance the atmosphere of the game, not the power of the magic-user. No effect as powerful as even a first-level spell should be allowed.
To prevent players doing just anything with these subsidiary powers, and also for the sake of consistency, all magical effects should reflect the spells that the magicuser already knows. Xeno, incinerator extraordinaire, can dispense with flint and tinder to light his pipe. Corvus the Conjurer (who knows levitate, floating disc, and his own version of magic missile: telekinetic fist) can shuffle cards with psychokinesis. Maximus the Black, who knows death spell, can kill small harmless animals like mice merely by stroking them (he’s not bothered by flies or mosquitoes, either, as they die upon touching his flesh).
It is worth repeating that these effects are only for atmosphere. They should not be useful in combat. Tantalus the Beguiler (who knows charm person) can probably haggle a good price on a new horse, but if he is jumped in a dark alley and cannot bluff his assailant, he must resort to his dagger. Supernatural panache is a useful thing to have, but it is not a suit of armor.