Custom Spell Rules

[Windy]

Today I had an idea for a campaign setting in which the player characters are the first beings in the world to be able to use magic. I thought it would be fun to have the players run around introducing magic to a waiting world, with the after-effects sometimes coming back to bite them! But then I realized that a system like D&D or Pathfinder builds magic-using classes on the assumption that magic is an established system with rules, standards, and boundaries which govern how magic is cast. There are set lists of spells available to different types of casters, and straying outside of your lane is, in most cases, strictly verboten. If a character is supposed to be "inventing" magic, then why do they have to be limited to the spells listed in the book? The reason it would be so cool to play this campaign in the first place is being able to say, "See that 'Speak With Fruit' spell right there? Yeah, I invented that. No, I don't really use it a whole lot, but we did use it one time to uncover an assassination plot at a royal banquet."

I'd like to get your thoughts and recommendations on which systems most easily accommodate custom spells. Are there any which are designed specifically to allow or even encourage custom spells? Alternatively, if I were to use Pathfinder, is there some suggestion which would make the official guidelines more concrete? I'm not necessarily looking for a comprehensive system (though that would be awesome), but a few numbers would be nice to at least add a pretense of balance.

[Leviting]

well, there are the epic spell creation rules in the SRD, though I don't think there is a way to determine a spell level for them besides, well, epic. You could work off of it, though.

[Ravens_cry]

Ars Magica sounds like it could fit. You'd have to tweak or even throw out the setting as fits your needs, but it is my understanding that quite a lot has to do with researching spells and such.

[endoperez]

Ars Magica relies on its magic system. Using it for other stuff is, at times, a bit clunky. If you want your PCs to do stuff besides magic, you can still look at it for inspiration but there could be other verb+noun magic systems out there that work better for you. Many are homebrewed to work on existing systems, so you might be able to find something that works well with D&D or whatever it is your players are familiar with.

Spoiler: Ars Magica TL;DR

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So, in short, ArsM is a skill-based and verb+noun based magic system, where there are like 15 skills for different magics. Of the skills, 5 represent verbs and 10 represent nouns. To heal, you use the "Create" verb and either "Human" or "Animal" nouns. To harm, you can use "Destroy" verb and a target-appopriate noun, or you can "Create Fire", or "Command Earth" effect that tells a boulder to crush a target, or "Change Water" to transform rain into acid, and so on.

There's a long list of base effects. To cast a spell of that effect, the sum of your appopriate skills + dice have to equal or exceed that. Adding a longer range, more targets or a longer duration to a spell will increase the target number.

Then there's rules for researching spells, vs using weaker effects spontaneously, and so on.

4th edition of ArsM is free on some web shop somewhere, so you can look it up if you're interested.

[SiuiS]

Epic casting (epic level handbook, 3.0) is actually fairly consistent, with the spell craft DCs of spells being based off the level of a similar effect. I had a chin who reverse engineered the base numerics and was able to use it as a guide for high level spells.

You can use that in play; casting a burning hands would be based on having enough spell craft to make the roll, based on casting and mitigation and such.

[Rhynn]

Adventurer Conqueror King System (ACKS, see sig) has rules in the Player's Companion for creating spells, based on the spells of B/X D&D (basically, most existing/traditional spells end up on the appropriate level with these rules). It's a D&D retroclone, so they might even be useful for other D&D games, but don't bank on it.

Unisystem has rules for improvisational magic in Dungeons & Zombies.

The Riddle of Steel magic system is based on improvising spells based on some principles, although you can also codify them. It's a punishingly tough magic system, though - all magic ages you as you use it (the base unit is months; you could change this, though), and magic isn't easy. For instance, if you create a spell that flies you through the air at 400 mph, your body will break down and hitting a bird or other random object would mess you up... and you wouldn't be able to breathe, either. So you need to also create a shield around yourself and magic some oxygen into your lungs.

[SiuiS]

Mage: the awakening is a good system, too. It's probably too broken for a fantasy game though, since first level magic makes you the world's greatest detective forever.

[HammeredWharf]

I don't know how well it works, but Pathfinder has the Words of Power system.

[mikeejimbo]

The standard GURPS magic system is widely considered awful. However, due to that there is an entire book for alternative systems, including multiple verb+noun systems and a way to make a Mage-like system. Even if you don't want to play GURPS, GURPS Thaumatology could be an inspirational resource.

[Windy]

Thanks for the suggestions! I will have to sit down and have some quality time with a few of these. I'm intrigued by this Verb+Noun business, but won't be able to really read up on it until after work... And after some thought I realized that players will just try to make the most generic spells possible, since it would give them the most bang for their research bucks. Do any of these systems cut you a break for making a spell more specific? For example, Speak with Fruit being more specific than Speak with Plants, it would also have a lower research time and component cost. Maybe that even translates to a lower-level spell, too, but power level isn't as much of a concern as making sure players have incentive to make a variety of spells and effects.

What kinds of spells would you guys come up with if you were a player in this campaign? We've got a few staples like Light, Magic Missile, Create Water, etc. What would you invent to fill out the rest of your spellbook? Let's assume that spells have to be at least as specific as the average entry in a Pathfinder/D&D spell--you have to limit potential targets, range, etc. What kinds of effects would you find most useful?

[Jay R]

Fantasy Hero does exactly what you want. I once created a bard whose spells were songs, so they were all built with an area effect which was dependent on ambient noise, three minute casting time, no effect on the deaf, with his harp as a focus, requiring gestures and speech, etc.

(I also created a cantrip Tune Harp, which I assume any magical bard would have.)

A lot of people don't like it, because creating effects requires some basic math, but I've had lots of fun with it.

[mikeejimbo]

Certain of the GURPS systems work like that too, especially if you're building magic as Powers. Ritual Path Magic also works similarly, but also requires even more GM oversight in vetoing certain effects.