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Designing a poorly controlled magic system


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I am looking to design a magic system where magic cannot be easily controlled and it is realtively easy to loose control of magical energies. The current idea that I am working with is something like:



Roll of 3: Overpowered results, effective active points & advantages double in spell or other very excessive effect (GM's choice)

Roll made by 4+: 50% increase in effective active points and advantages in spell or other excessive effect (GM's choice).

Roll missed by less then 4: Fizzle, pop, Sparks or other some sfx.

Roll missed by 4+: negative effect similar to mad by 4+.

Roll missed by -10 or rolled 18: negative equivalent of rolling a 3.


Does anyone​ have any better ideas on how to better capture this chaotic wild magic effect?

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Required Skill Roll + Side Effects as required modifiers is pretty much the standard method of handling this mechanically. Sometimes this kind of thing also gets done with Magic Systems were you buy spells as individual skills (buying Fireball ​11- for 3 CP instead of Fireball​ as an AoE Blast Xd6 for Y​ CP for example). If you don't want to deal with making 'perfectly legal' constructs, you could instead estimate how limiting or advantageous being subjected to your random effects chart is given the player's average likelihood of success, and then assign that value to a bundled "Wild-Magic" modifier taken by all spells.


Regarding the effects of exceptional successes/failures, you could look at any of a number of old D&D Wild-Magic tables for inspiration.

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Random us always the most difficult thing to pull off - systems always feel ordered and efforts to get random often have a different feel in game.


I wish I had a decent suggestion. It feels to me like there needs to be a dice solution, one that is easy to read.


In my head I see something like six dice. If you use a spell and roll effect dice the three of the dice will be red, three will be green. Match sixes in each colour, more red sixes means bad things, more green sixes good things happen. Other dice can be rolled if necessary... :-)


This still feels a bit clunky to me. Custom dice might be better, if one side of a single die is red and another is green then your 3D6 roll can show anything between three greens and three reds without necessarily being tied to 1s and 6s. I would like to have enough dice like this such that I had one where each number was covered by red and green and the first randomness would come when three of those dice were chosen to roll my 3d6....

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Side effects and skill rolls, plus more random levels of results (instead of granting 5 PD/ED resistant protection the spell grants d6 of each all give a more uncontrolled feel.  Adding in environmental effects where an area causes extra side effects, boosts magic, or reduces it (or changes from phase to phase or turn to turn) can make things even more chaotic.  Throwing luck and unluck in can make things more interesting as well, with very powerful mages having more dice of luck so they can control things in their favor more often.  Treat each level of luck or unluck as x active points of results for side effects.

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RAW, I'd go with the already suggested Skill Roll + Side Effects route.


As a house rule, I've toyed around with the following idea that might work if you want magic to be mostly predictable but occasionally weird:


All spells require a Skill Roll to cast.  If the roll passes, it works as designed.  If the roll fails, the spell is not cast but END/Charges, etc are expended.  If the roll comes up triples, something odd happens.  If the roll succeeds, the odd thing is beneficial (or, at worst, strange but harmless); if the roll fails, the odd thing is dangerous.  The specific effects would be rolled from an appropriate table made up by the GM.  This would be worth no points as you can get either good or bad effects when weird stuff happens.

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This is specifically for a post apocalyptic campaign (ie: Thundarr) that I am developing. Magic has returned to the world but, unlike most fantasy worlds, there are no magic colleges or long term spell development. Casters generally have to figure it out for themselves. Controlling magic is like fishing with dynamite while blind folded; crude but generally effective if you throw it correctly. The assembly of magic spells I'd like weaving​ of threads that could unravel before the spell is complete, or slip a bit, thereby resulting in the quirky or disastrous effects.


This is the dealing that I am trying to capture.

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for a keep the powers low you can also go with-

15    Multipower, 60-point reserve,  (60 Active Points); all slots Requires A Roll (Skill roll, -1 per 5 Active Points modifier; Must be made each Phase/use; Magic skill; -1 1/2), Side Effects (-1), Gestures (-1/4), Incantations (-1/4)


1      fire ball:  Blast 8d6, Area Of Effect (8m Radius; +1/2) (60 Active Points); Requires A Roll (Skill roll, -1 per 5 Active Points modifier; Must be made each Phase/use; Magic skill; -1 1/2), Side Effects (-1), Gestures (-1/4), Incantations (-1/4)


deadly for the user, that is -12 to the roll

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I'll have to second Netzilla's general idea, and reinforce that it doesn't seem like you're describing a system where spells can just fizzle or BANG!, but where they just may not work as intended always. Therefore slapping on Side Effect onto spells, and then let success or failure decide whether the "weird" is beneficial, indifferent, or negative, with you rolling "effect dice" behind the screen to determine just how "bad" it is. That would allow -you- to throw in something like instead of the fireball just being bigger on a great success, maybe it's actually smaller....but took on Indirect and just bypassed the wall the targets were hiding behind. That "Cloud of Fog" the caster tried to put up? Yeah, no, it's a "Cloud of Butterflies"! Same penalties to seeing through it (there are a -LOT- of butterflies), but it let's you have some fun with the "Holy crap, what was that!" factor.


Just make sure that your potential spellcasting players understand that, "Weird stuff is going to happen."

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Interesting thoughts... I would recommend the following ideas:


First, consider that in 3D6 the range of divergence from the bell curve's apex (11 or less) is pretty low. +/- 3 already makes a huge difference. You'll want to consider that when assigning chance of failure.


Here's a simple table that shows you what the chances are of rolling a specific number on a single throw of 3D6. This is what measures your difficulty. It's noteworthy to see that trying to roll 14- is already at 90% chance of success, while 8- is at 25% chance of success. This is why I believe your +4/-4 may be too far off the range for minimum results. You'd very rarely, if at all, see the effects.


 6- : 9.26%

 7- : 16.20% 

 8- : 25.93%

 9- : 37.50%

10- : 50.00%

11- : 62.50%

12- : 74.07%

13- : 83.80%

14- : 90.74%

15- : 95.37%



The rest of the ideas I am making up on the spot. Use or modify at your discretion/heart's desire:


A. I would suggest a fixed magic roll threshold number, based on how hard you want the control to be. This would be based on the typical -1 to skill roll for every 10 active points in a spell.


For Example:


Small spells, with only 10 or 20 Active Points, would only warrant a -1 or -2 to their rolls. Let's say, for the sake of the example, you have set your fixed failure roll at 14-.


For these easy spells, the final success rolls would fall into the 13- or 12- range. That is easily doable, in the 83% and 74% success chance range. That's pretty good, since these are easy to moderate spells. I am imagining that these sorts of spells would rarely fail, or if they do, would have moderate consequences.


The higher the spell's power, the harder it will be to make that success roll. Spells at 30 AP have an 11- or less chance, spells at 40 AP have 10- chance, and so on.


B. Assign your difficulty based on your fixed threshold roll. 14- seems good to me for a common system with powers in the 40 AP range as strong, anything above it as very powerful. (60 AP spells in Fantasy Hero are pretty strong, in my opinion). You can lower the fixed threshold number by 1 or 2, to 13- or 12-, but you'll be making casting spells very hard, meaning that it will be easier to get failure results instead of success results. Raise it if you want to make casting spells easier.


C. If you want to reflect different skills between casters, you can have them buy pluses to roll on the casting skill. Because magic is supposed to be uncontrollable, I suggest you make those pluses be very expensive, reflecting either great study, or mastery of a very difficult subject. I would recommend 10 points for each +1 to the skill. It's enough to give any player good pause, and have them see it as a significant investment. You can make it higher or lower depending on how hard you feel it should be. Of course, perhaps in your game world it is not possible, so players may never be able to get it on their own...


D. ... which leads to the idea that perhaps such a thing is possible but with magical items that grant the user temporary bonuses of +1 or +2, either by charges, limited uses per day, or which ever way you feel this ought to be handled, but not unlimited.


E. Finally, the ranges of failure and success side effects need to reflect your dice probabilities. 


I would recommend the following:


Difference by 1: additional cosmetic effects or very minor side effects, nothing that will actually change the result

Difference by 2: small side effects, perhaps spell power alteration by 25%.

Difference by 3: moderate side effects, perhaps spell power alteration by 50%.

Difference by 4: strong side effects, perhaps spell power alteration by 75%.

Difference by 5 or more: catastrophic/extraordinary side effects, 100% spell alteration, GM fiat


Note that difference of 1 is just cosmetic (extra sparks, colors, wild flowers, what have you). A difference of 3 already starts to get dangerous, and a 5 or more is utter ruin or surprise, where the character will probably be looking at his own fireball straight in his face, a rain of fire, or whatever you feel is appropriate. Based on the chances given in the previous table, you can make the results weaker or stronger if you shift the numbers up or down by 1, maybe 2 if you'd like. This difference does not have to be the same on the failure and success rate. You can shift the failure down and the success up higher if you wish to lessen both effects, or only success down if you want to see more "extra effects" if a caster succeeds.


You can achieve the same effect by changing the casting roll penalty by a different Active Point threshold, like -1 per 8 AP, or -1 per 5 AP to make it harder, or make it easier by raising it to -1 per 12 AP, or -1 per 15 AP, your choice depending on how powerful you want to make your mages.


So, those are the ideas that came to mind. Feel free to cherry pick them, rework them, what have you. I still think that the base numbers I quoted you in the example will work wonders for your "unruly magic power" system, in that you will get easy to manage spells at a lower AP level, and hard to manage spells at a higher AP level, without things getting out of hand. You'd see a lot more small or medium effects, because it is easy to get those in the smaller range, and very few huge effects because it is hard to roll those numbers. But in general, you'd be seeing some sort of effect (good or bad) very often. This would reflect a broad unpredictability in the magic stream. (Remember not to cross them.)


Consider the dice probability table to see how frequently you'd like to see success and failure based on different casting rolls, and then pick spots for where you think it would reflect your desired magic feel.


Adjust as necessary. =)

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Interesting thoughts... I would recommend the following ideas:


First, consider that in 3D6 the range of divergence from the bell curve's apex (11 or less) is pretty low. +/- 3 already makes a huge difference. You'll want to consider that when assigning chance of failure.

Thanks for your extensive response. My group is all D&D players who don't currently understand the Hero System spell/power creation and therefore we are using the spells from the Hero System 5th edition Grimoires I & II. I am using -1 / 20 AP for the magic roll as a -1/10 seems a bit high to me especially considering the wild magic effects.


In my campaign, magic is based on the weaving of magical threads to create desired spells. The threads are slippery and akin to knitting with wet spaghetti noodles and sometimes the spells shift a little or a lot but not.to the.point of spell failure. I am looking to put together a system where magic can be unstable at any time, not just on a failure. I liked an earlier post suggesting that on rolling 3 of kind on the magic roll, regardless of success, results in spell slippage. I developed this to include the idea that on a roll of 3 of a kind the player rolled an extra die to determine if the Minor Side Affect (or Major on a critical) manifested; positive, negative, or neutral. I didn't do the math at the time but your post inspired me to look into this. It turns out to be about 2.7% of 3 of a kind occurring. 10% seems to be a better number to me.


I also want to keep the number of dice rolled to a minimum as I am already getting some flack of having to roll to activate spells and spell to hit rolls (unlike D&D!) :/

I need to mull this over further. Perhaps, make double use of the Magic Roll where two of a kind (same color dice) results in slippage (16% chance) and the third different color die used to determine the positive, negative, neutral result while the total if the 3 determine actual success or failure.


Thanks for your suggestions

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As for the magic roll, give them a choice, either make a magic roll or pay additional END. Cannot remember the limitation for giving a spell a magic roll but if it is +1/2, and all spells regularly take 1/2END, then they make a magic roll or choose to cast automatically but take full END cost rather than 1/2 END.


Players like a clear choice, even if it is limited.



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Plaid Mage-"Nicely done, Cardigan Mage!"

CM-"Thanks awfully, PM, old man! Now, if you don't mind, I'd like to throw an Improved Lightning down the gully we've blocked. Carrion Ooze are vulnerable to electrical damage, and the conductance is set up perfectly!"

PM-"Jolly good, CM! Let's see some sparks flying! Tally ho ipso igitur, as we used to say back at old Brasenose!" 

CM-"Er, well, yes. It seems as though I'm in a bit of a quandry here. You see, I haven't cast Improved Lightning since I found it in that old spell book and inscribed it, and. . . "

PM-"And you're having trouble finding where the UI put it! I know the feelling. Well, two noggins better than one, as the ettin archmage used to say. Drop it down so I can have a look!"

CM-"Here it is."

PM-"Mouse over to the drop down Action menu."

CM-"Well, actually --Ouch! Dash it, now I'm going to need a rabies vaccination!-- I tried that. It turns out that most of my new spells on this level aren't under the Action menu at all."

PM-" Well, here's a neat little trick. See the Execute option? You see that tiny little icon? The one that looks like a point of green? Well, it turns out that that indicates that the menu isn't empty anymore. Mouse over to it. Here, use mine, it's more docile."

CM-"I tried that. See? Two sub-menus have shown up: Movement and Adjustment. Neither seem likely to hold Improved Lightning."

PM-"Have you looked? Why don't you --Oh. Why is there a password prompt now?"

CM-"I don't know, but I'm waiting on IT and --there we go. Unlocked. See? Improved Flight. And Flight? I didn't even realise that it had been moved. Why isn't Dimension Door here, too? And why are all the cleaning and mending cantrips in this menu all of a sudden?"

PM-" Time for desperate measures, old chap. Mouse over to the Help menu."

CM-"Have you ever looked at the Help menu? Let me quote the introduction: 'Available apps are denoted by signifier in their respective ASID with SIFs. Access their PV Number for topic-specific help."

PM-"I like the comic sans font on yellow notepaper emulation. That really says, 'professional.' So if you zoom out a couple times, you'll see that there's a number in the icon field in the menu window. Could that be a PV Number?"

CM-" Could be. Here let me use the keyboard to enter it."

Banyan the Bard: "I was using that."

PM-"And the Help subtopic is empty. Lovely."

Banyan the Bard-"Have you tried dropping all the submenus down randomly? That kind of stuff works for bards."

CM-"Pfft. None of the other icons have changed. So there's nothing new in their menus--"

PM-"What have we got to lose? Ah, here. Under Save. Saving Throws, Healing spells --good thing  the cleric's upright, we'd never have found those-- And Improvements, which, ta-da, Improved Lightning!

CM-"I'll just mouse over to it and --I''ll just mouse over to it again while squeezing the mouse so it doesn't disappear, and--Ouch! Drat it!"

PM-"Another password prompt? And IT is offline, I'm going to hazard a guess?"

PM-"Seems so. I sure hope another tech picks up before the Carrion Ooze gets its Recovery Phase. In the mean time, haven't you got some regular lightnings that you can throw and-- then we can watch in frustrated amazement as you fire Magic Missiles instead."

Banyan the Bard- "May I suggest running away now?"

CM-"I'd cast Improved Flight, but it's probably password-locked, too."

Banyan the Bard-"Less talking, more running."

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I like your idea of using the magic roll, taking the doubles, and then using the third die to determine how far off the norm the spell went. Brilliant. =)


I have been mulling this over and after some thought, it seems that this is not the best idea. The use of the 3rd die as a "wild" die seems that weights the values of the overall die roll as to how the magic goes wonky (positive, negative, or neutral). It seems to me that using 2 matching dice for pairs and then a 4th die as the "wild" die makes the overall distribution of wonky magic more uniform. I haven't worked the math on this, but it feels better to me. This is still a work in progress so I might go back to the 3rd die as a wild die option but for now.....

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