Temperamental Magic (5e Variant Rule)
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All magic is formed of three components, the Vocal, Somatic, and Material, each used to determine what effects go into the casting of spells. But spells have been refinined from their initial versions, changing and shaping into the spells we know today. Some sacrifices had to be made to keep the stability of the spell together, but what if you don’t care about how stable a spell is? What if you wish to delve into the deep guarded territories of a person's mind with ease with Detect Thoughts? Or curve your cast with Firebolt? Regardless of what you do with your spells, they must at least bear some semblance to the goal, or the spell will fail.
Temperamental spells are variants of the base spells determined by the DM once discovered by the players. Adding this style of casting to the game requires a lot of thought and extra work, but personalizes all magic. Regardless of the spell however and how it turns out, casting a non-basic spell (known as a Stable spell) results in the spell having a chance to fail, rolled on a d100. This number must be rolled equal to or greater than to have the spell be cast with it’s new changed effects. Here is the equation for determining whether or not a spell can be Temperamentally cast:
(((Spell Level+1)^2/L),rounded up)-(Spell Caster Level,rounded up)
As seen above, the Spell level and spell caster level have a massive effect on whether or not a spell can be temperamentally cast, alongside the Likeness to the base spell, L. L is scaled on a 0-1 scale, with 1 being exactly the same, and therefore stable and unneeding of the equation, or 0 meaning the spell is nowhere near the base spell, and therefore uncastable with the goal in mind. Strive to keep this relatively close to the main spell’s likeness, and your temperamental magic casts will stay relatively castable. Stray too far however, and your magic will never work. Failed temperamental spell casts do not consume spell slots, only the actions used to perform them and materials used to cast.
Also notice how the rounded up portion of the spellcaster level is there. this is to make Half and third casters able to have temperamental casting as well, but as they are not the most magically proficient, get reduced down a certain amount for their casting of temperamental magic. Half Casters have their level halved, and Third have their level divided by 3
Examples of Variations and what each Component may affect
Firstly, let us get an example to set the scene for how our temperamental magic casting works. Let's assume we are a 5th level Wizard who just picked up the Fireball spell but would like to tamper with the spell's effects. This baseline setup gives us these equations:
Fireball as a spell requires every type of component, Vocal, Somatic, and 2 Material Components, those being a tiny ball of bat guano, and sulfur. How can we change this yet still get a desired effect?
The vocal components of a spell are the main component of a spell. Changing these words may have massive effects on the likeness of a spell. For instance, adding the words Delayed Blast changes the spell into a 7th level spell, increases its damage, etc. Words have huge effects on the goals of the spell, and therefore may hugely change the style of the spell. Likewise, if the spell level cast changes, so does the roll required. To cast varied spells, you must be able to supply the spell slot required. For now, let's instead think of Compressing the ball to deal it’s damage in a smaller range but heightened. We’ll call this Compressed Fireball
Like Vocal components, Somatic components tend to determine the shape of a spell's effects. For Fireball, it’s rather simple, just point your finger and the ball shoots out towards the determined spot. However, what if you do a lob motion with your point? The spell may now volley, but your likeness variable and range, due to the lobbed motion, will suffer because of it. Changing the somatic components will typically cause the motion and style of the spell to change. We’ll call our now varied spell Lobbed Compressed Fireball.
Materials are very vague in terms of what’s required. Specifying the type of something, such as bat guano does limit our choices, but you can divulge a fair bit as long as you have a good enough likeness variable. You must always provide material counts equal to the amount of materials required by a spell. Therefore, with Fireball, the spell requires a minimum of 2 components to cast. Using an Arcane Focus or Holy Symbol nullifies the usage of this to vary your spells, therefore if you are interested in Temperamental spells it may be better to deviate from the normal Arcane Focus. What makes a spell stable is not only it’s unlikeliness to fail, but also the fact that if the spell has material components that are not specifically consumed, the stable spell never consumes materials, meanwhile a temperamental spell always does. Changing your materials up may cause it to vary drastically. Maybe changing the bat guano to pigeon guano will cause the spell to have a longer range, or the sulfur into the more flammable reactive hydrogen causing higher damage, etc. Of course, this all revolves around your likeness variable, and the more changes you cause the more unlikely the spell is to work. We’ll add pigeon guano and a vial of hydrogen to our current spell to get Distant Explosive Lobbed Compressed Fireball. With a tongue twister like that, I doubt it will work very well.
Testing the Spell
Our Distant Explosive Lobbed Compressed Fireball is quite a crazy spell. We’ll pull back out the equation for usage here and ask our DM about casting the spell in a fight. Here’s what we know, and here’s what the DM determines our likeness variable to be.
As you can see, our likeness variable is based on an average from all the effects we have used thus far, and our hydrogen usage might be a massive savior when it comes to our roll. We did however only make something with a likeness of a 0.6, thus we still might not cast it. Here is the required roll equation in full.
As you can see, it did have a massive effect on our casting capability, as we now must beat a 22 on a d100 when attempting to cast the spell. Temperamental variants count as their own spell and must be learnt/prepared separately. If the spell cast fails, it triggers a wild magic surge, and components are consumed, action is spent, but spell slot isn’t.
Managing Temperamental Spells Components
A good recommendation for your temperamental spells is to form three maps and set them in a triangle formation of each other. These three maps for the Vocal, Somatic, and Material components. You may then use the maps to organize any components you can think of or are needed to cast a certain set of spells, and use distance from the original stated items to help determine the Likeness variable. The closer the better basically, and each step on the map away the less equivalent to the base for, and therefore closer to 0 your likeness variable may be. Likewise, if a component is so different, the DM may force the likeness variable to become 0, such as attempting to cast Fireball with Ice. Vocal components should be organized by element or goal on your map, somatic components being organized by complexity of motion, and materials being the most categorized because it is categorized by whether it comes from a living animal, cost, color, and relation to other materials.