What in your eyes makes a good magic system for a tabletop roleplaying game? How is this different from a magic system for a story like a novel, television show, or comic book? You can answer in terms of mechanics or in terms of lore. You can answer with a magic system you made or someone else made.

For me, a sound magic system is one that offers freedom with a fair amount of thematic limits- such as 'No reviving the dead' or 'No time travel', and a cost to using the power. One example is Exalted's Essence. It has the same limits that I outlined, it costs 'motes' (think: MP from various JRPGs), and it can do a lot of things like create an army of skeletons, allow the user to cleave through mountains, and so on and so forth. It is limited by the type of being using it- Solars cannot shapeshift, Dragon-Blooded have weaker powers but are strong in numbers, and so on. This shows in both lore and mechanics. In addition, the world and story should be built around its inclusion in an organic way.

I also have my own system based on this design principle. To put it simply, it works like this:

-Magic-user makes a clear image in their head with their imagination (they imagine a fireball)
-Reality is then hacked to fit that image (the fireball appears and shoots)
-Their stamina is depleted depending on the power of the desired effect (making a fireball the size of a skyscraper would take a lot more energy than making a fireball the size of your pinky), at the same time as step 2

Also, 'game/story-breaker' spells you find in DND would require a good amount of power to use. For instance, 'Create Food And Water' would cause most people to pass out after just two uses. 

For me it's important that magic be mysterious and strange. I don't need to know its limits or how it works. I'd prefer not to know. Secrets can be discovered as the game is played. There are people, places, things that have magic and that can share it.

As for mechanics, I prefer the kind that add some uncertainty, like DCC RPG. Roll a result on a table with some tweaking of modifiers perhaps. This adds excitement and makes magic feel more magical. As for Vancian magic, I try to elevate it a bit when I GM, adding fluff or encouraging the player to add fluff when casting a spell. My go to hack is to offer the player a deal with a d20. 2-19 and the spell goes off as written. Roll 20 and you get double the effect. Roll a 1 and bad stuff happens.

I like the magic/miracles/psionics etc systems presented in D6 Fantasy, Adventure, and Space. Each needs your setting specific limitations and thematics added before use in anything but a movie night one-shot, but it is a system that quantifies what it takes to bend reality, and its adjustable as needed to fit exactly the tone and theme your game requires. I guess simulationist might be the word, but like most anything you do with those books it works best once you tailor it exactly to your needs.

For me a good RPG magic system is one that makes using magic (or the comparable form of supernormal powers) something you have to make interesting tactical decisions about, allowing players to make meaningful trade-offs between power, cost, speed, flexibility, risk and convenience. The greater the effect, the more it should cost the user in terms of energy, resources, time and preparation effort, and the system should allow players to trade off between these.

The Riddle of Steel and Barbarians of Lemuria both in their own way aspire to this, though neither (in my own not-so-humble opinion) quite achieves my optimum version of it.

It needs to feel mysterious and arcane.  Otherwise it's just superpowers or munchkin bullshit.

Quote from: David Johansen on December 28, 2022, 11:36:55 PM
It needs to feel mysterious and arcane.

Do you think any existing published systems successfully accomplish this? I like the "mysterious and arcane" feel as well, in principle, but I admit I can't think of something well-enough designed to keep players from devolving into the purely game-mechanical aspect of it.

Even GURPS Cabal, I think, ultimately runs into the Catch-22 that anything organized, consistent and reliable enough to be a viable game mechanic is going to be predictable enough, once mastered, to lose some of the mystery and grandeur the outsider or newcomer will experience.

"Magic Systems" are irrelevant without the setting stating the expression of magic.

I don't like Magic for Magic's sake. And just tacking on some justification for characters to shoot lighting bolts out of their asses with nothing more than decreasing "spell points" without any context.

It might be a trope - but the trope has to exist for a reason. The system should mechanically express that.

Quote from: Stephen Tannhauser on December 29, 2022, 12:53:15 AM

Quote from: David Johansen on December 28, 2022, 11:36:55 PM
It needs to feel mysterious and arcane.

Do you think any existing published systems successfully accomplish this? I like the "mysterious and arcane" feel as well, in principle, but I admit I can't think of something well-enough designed to keep players from devolving into the purely game-mechanical aspect of it.

I think it needs to be more about the process than the results.  Personally the endless list of minor spell variations doesn't do it for me.  Mechanically Worlds of Wonder Magic World, GURPS Magic, and Rolemaster Spell Law are my favorites but they're all pretty cut and dried.

I think D&D is one of the better systems for mysterious and arcane.  You've got this book of weird and unrelated spells that are fiddly and arbitrary in their effects. You've got weird limitations on how you prepare and use spells.  Unexplained names like Tenser and Bigby keep showing up.

I've always thought Dragon Quest was decently evocative once you got passed the elements into summoning and black magic.  Fifth Cycle had a pretty neat magic system where the spells are in this kind of interlocking and overlapping wheel.

My own attempt, The Arcane Confabulation uses pretty structured and mechanical spells but tries to deal with them in terms of how they are accessed and used.  Much like a combat system might break using a sword down into strikes and parries.

I feel like a game focused around magic works best when all PCs have it and it's more freeform in casting flavor, with different folks having different casting styles and possibly even magical worldviews. That said, I'd also say that a cost and skill requirement that varies based on effect type and magnitude is generally preferable for me. That way folks don't try to cheat the system via technobabble process or one-off spells/abilities/charms/whatever that are poorly balanced and hence spammed and/or otherwise abused. Dice pools and tallied successes are my preference, since that way if you're more skilled you're less likely to screw up randomly, and there are some things that only a skilled practitioner can both do and do reliably. That said, I also like balancing risk and reward, so maybe also a mechanic where you have to declare what you're attempting ahead of time, and DM decided or randomly rolled botch effects come into play if you don't get enough successes. Keeps magic feeling a bit more uncertain, mystical, and risky rather than just like a vending machine. DM adjudication is still important more generally, tho, cuz no matter how good the system folks will try to break it, either within or outside legit interpretation of the rules.

The main difference for a novel or tv or whatever being that things need less definition and quantification. Magic can be more mysterious in its mechanics because we don't have to play with it as a quantified stat setup at the end of the day.

Let me start by observing that magic systems are almost never all purpose; they are optimzied either to enhance the worldbuilding, the storytelling, or the gameplay. Rarely you will see magic systems touch all three or do two of the three, but more usually a magic system is trying to do only one thing. This leads me to my first observation:

A good magic system knows which one of the three objectives its trying to accomplish, and if it is aiming for several, it has a plan to get there.

Consider D&D's Vancian magic system. This is clearly all about gameplay; it's optimized to minimize bookkeeping, maintain the game's ability to remain balanced (actually being balanced is a different matter), and to create opportunity cost. All of those are gameplay decisions.

At this point I think "Wild and Unpredictible magic" systems are overdone by about 15 years, and I prefer players to think ahead and anticipate the consequences of their actions, anyways. The magic system in my homebrew system, Selection: Roleplay Evolved is technically advanced alien biotechnology with telepathic interfaces. It is completely diceless, uses a unified cooldown bar, and is completely deterministic. The worldbuilding is actually following the mechanics here; randomness dilutes the value of a strategy game, so RNG had to be  curtailed as much as possible on the outset. No RNG magic creates cognitive dissonance in players unless you explain it in a different way.

A good magic system is fit for purpose. Avatar elemental bending magic is not compatible with console JRPG spell spam is not compatible with medieval authentic magic.

What does it need to do for the game & worlds and how well does it do it? Internal consistency and thoughtful ramifcations are all good, but does it fit?

For crunch heavy combatant magic I would like Mekton Zeta beam weapons on  energy pools reskined. For player fun of exploiting the magic in character, I actually like oWOD Mage 2E as it is fun to "cheat" reality by applying real world engineering, the meta plot stuck up WW's arse be damned.

I prefer seeing lower level magic in an RPG.  Perhaps 3rd Level spells, should be a capstone achievement?  Knowledge of such magic, and the required methods and components; should be scarce, and limited.

Just a thought.  Maybe E6, isn't such a bad idea?

For me it's a game that has more than one.  Each system distinct from the others. 

For example.  Palladium Fantasy.  It has classic spell magic, or elemental wind/fire/earth/water magic, or magic circles you paint on the ground to control things and make land mines, and wards you paint on things to give them buffs.