This is the first in a series of posts that will deal with the Laws of Magic. These Laws are not codes that govern the conduct of magic-users -- they're laws in the scientific sense of the term -- cosmic "rules" that dictate the behavior of magic in the campaign world. The purpose here is not to over-complicate magic in D&D campaigns, but rather to offer new and interesting ways to terrify PCs.
Tambraal's Law: That all magical works act in opposition to the lawful flux of time and space. That this flux exerts a measurable toll on the integrity of all magical works. That this loss of integrity (i.e. the slow dissolution of magical bindings) inevitably leads to a loss of efficacy. That this loss of integrity also potentially leads to unforeseeable hazards.
Tambraal's Law, also known as the Law of Disintegration, describes the process of magical decay. Over time, all magics begin to succumb to "pressure" from the lawful mechanisms of the cosmos -- the Natural Order of things. This Order interprets all magical effects and items as anomalous errors which must be corrected. "Correction" is a process that can take aeons to completely annul a particularly powerful magic as it erodes the bindings which hold that magic together. When these bindings give way, the magic loses its efficacy and may eventually become distorted. Magical distortions could exhibit themselves as harmless little side-effects. In the worst case scenarios, they become lethally dangerous glitches.
How Old Is That Item?
Every magic -- be it a spell or an enchanted item or an artificial being such as a homunculus -- has a lifespan. No spell is actually instantaneous. Even a magic missile leaves something of itself behind after its energy leaves the magic-user's fingertips: the harm it has wrought on the target. Even illusions have a prolonged existence in the memories of those who witness them.
In order to determine the projected lifespan of a given magic, we must take its creator into consideration. The manufacture of magical items is the milieu of experienced magic-users and magic-using entities such as gods and demons. The greater their experience, the more secure the bindings that hold their magical creations together will be. This fact puts the work of mortal wizards in a wholly separate class than those magics which are created by immortals. A three-hundred year-old mage, venerable as he may be by our standards, cannot hope to produce an item with the longevity of a divine implement.
Another important factor is the potency of the magic in question. The relative power of the magic works against the experience of the creator. That is, the more powerful the magic, the more difficult it is to maintain over time.
Use the formula below to determine the spell's or item's Magical Half-Life (MHL):
MHL = [(XP level of the caster) x (1000 years)] / [Spell-level of Effect or Enchantment]
The spell-level of the effect or enchantment might be an approximation (determined by the DM). For example, we can think of each +1 on a magic sword as a single spell-level. Try to shoe-horn effects into levels 1 through 9.
In the case of gods and demons it may be necessary to approximate their XP levels as spell-casters. Some gods may indeed be "off the scale" and in those cases I suggest the DM adjudicate just how much of the god's focus was bent on the creation of the effect/enchantment. A divine afterthought might be crafted with the efficiency of a 20th level magic-user, whereas an item intended to be a potent weapon against a hated enemy may represent the height of the god's abilities (100th level? More?)
I would suggest that most magical items the PC party comes in contact with be the creation of mortal wizards, most of them long-dead and forgotten in the mists of time. If you like, Read Magic may be used to ascertain the current age and half-life of an item.
Once the item/effect exceeds its half-life, it may begin to exhibit signs of decay. These magics have a 10% chance when they reach their half-life (and an additional 10% chance for every 100 years thereafter) to have a loss in efficacy. Additionally, they have a 5% chance when they reach their half-life (and an additional 5% chance for every 100 years thereafter) to become distorted. (Note: In the case of intelligent items, magical distortion has the side-effect of rendering the item hopelessly insane. Roll d4. Result of "1" or "3" means that the item's alignment is inverted.) Consult the tables below.
MAGICAL EFFICACY LOSS (Roll 1d6)
- The magic exhibits a minor loss in efficacy. In the case of a magic weapon, the loss is a one integer decline in its "+" value. In the case of a healing potion, there may be a one integer minus to its curative potential. An illusion may become less convincing. Animated skeletons may decrease in total HP. The DM will adjudicate what is appropriate here.
- The magic exhibits a moderate loss in efficacy. Same as above but exacerbated to a two-integer decline or minus.
- The magic exhibits a severe loss in efficacy. Same as above. Bump it up to three integers.
- The magic exhibits a critical loss in efficacy. Same as above. Bump it up to four integers.
- The magic exhibits a total loss in efficacy. However there is still a residual aura that can be detected and the item/effect may still be subject to distortion (see table below).
- The magic has become a longevity vacuum that drains the lifespan of items/effects that come in contact with it. Exposure (proximity of 10 feet or less) means that item/effect must save vs spell. Failure means a loss of 1d1000 years to total lifespan.
MAGICAL DISTORTIONS (Roll 1d6)
- Buggy: The item/effect only works properly 50% of the time. The rest of the time it [Roll 1d6] (1-3) doesn't work at all; (4-5) does the opposite of what it's supposed to; (6) does something completely random and harmless (i.e. Instead of throwing fire balls the magic wand throws mustaches).
- Minor defect: The item/effect produces a random side-effect that could potentially be harmful (i.e. Every time the +2 sword is drawn it produces a shrill screaming sound that can be heard for 1d4 miles around).
- Major defect: The item/effect produces a random side-effect that is totally hazardous (i.e. The illusory door exudes a poisonous gas that is only detectable magically).
- Serious Glitch: The item/effect produces random side-effects spontaneously (whether it is used or not) every 1d6 turns. There is a 2-in-6 chance that such effects will be totally hazardous.
- On the Fritz: The item/effect has become unstable and highly volatile. Even its shape (in the case of items) has become amorphous. It produces random synaesthesiac area-effects constantly (i.e. sounds have taste, smells can be seen, thoughts can be heard, etc.) The area of effect will be xd100 feet, where x is the item/effect's current age divided by 1000.
- Perilous: The effect/item has transformed into a x HD magic-consuming abomination, where x is the item/effect's current age divided by 1000. Any magics used against it to cause damage will instead increase its HP total. Only creatures and items with magical antipathy (i.e. an anti-magic weapon) will harm it.