⚡ Promptolis Original · Creative Arts
✨ Fantasy Magic System Rules Tester
Stress-tests your magic system for the loophole a clever reader will find in chapter 4 — and the off-page exploit your villain should already be using. Built on Sanderson's Three Laws plus 80+ published-magic-system audits.
Why this is epic
Most fantasy magic systems leak in 1-3 specific ways: cost-evasion (a character could just do X to bypass the cost), scaling-paradox (if magic works at scale Y, why doesn't civilization look different), or villain-incompetence (the antagonist hasn't done the obvious thing). This Original audits all three.
Applies Sanderson's Three Laws (understanding scales with utility, limitations > powers, expand existing rules over adding new ones) to YOUR specific system — and tells you which law your draft is closest to breaking.
Outputs the loopholes a smart reader will find, the off-page exploits your antagonist should already be using, and the 'scaling cliff' where your magic produces a world that no longer matches the one you've described.
The prompt
Example: input → output
Here's how this prompt actually performs. Real input below, real output from Claude Opus 4.
<setting-summary>Mid-tech fantasy world (think 1850s-equivalent — railroads, telegraph, no electric, no internal combustion). Continent of Vaerith, divided between three nation-states: the Crystan Republic (industrializing democracy), the Kingdom of Halgar (feudal monarchy), and the Tirenne Confederation (loose tribal alliance in the north). The world had a 'Sundering' 400 years ago — a magical catastrophe whose cause is debated. Magic existed before the Sundering and exists now, but is mistrusted, regulated, and rare.</setting-summary>
<magic-system-overview>Magic is called 'Resonance.' Practitioners ('Resonants') can manipulate one of seven 'Strains' — Heat, Cold, Pressure, Sound, Light, Tide, Memory. Each Resonant attunes to ONE Strain at age 14-16 (involuntary, unpredictable). Stronger Resonants emerge ~1 in 50,000 people; weaker ones are more common. Magic requires a 'Tone' — a hummed or sung pitch the Resonant produces — to manifest. The Tone is unique per Resonant per Strain. Tone-singing is exhausting. After major use, Resonants experience 'Tone-Drag' (1-3 days of physical depletion + occasional auditory hallucinations).</magic-system-overview>
<rules-explicit>1) One Strain per Resonant. Cannot acquire a second. 2) Tone must be vocalized — silent magic is impossible. 3) Range is line-of-sight or ear-of-sound (Memory Strain works only in physical proximity, ~10 feet). 4) Cost: physical exhaustion proportional to scale of effect. Casting beyond capacity causes 'Resonant Collapse' — sometimes fatal. 5) Magic CANNOT directly kill a person. It can incapacitate, manipulate matter, alter perception — but a Heat Resonant can't directly cook a heart inside a body. (Reason: humans have a natural 'dampening' field around their bodies that magic struggles to penetrate at lethal intensities.) 6) Memory Strain is heavily regulated — illegal in most of Crystan Republic, suspect in Halgar. 7) Resonance is genetic but not predictable; runs in families about 30% of the time.</rules-explicit>
<key-uses-in-plot>1) Protagonist (Tide Resonant, mid-strength) uses her ability to ferry illegal cargo across river borders by manipulating water flows. 2) Antagonist (Memory Resonant, very strong) has been altering people's recollections of a past political event for ~20 years to prevent uprising. 3) The 'Sundering' 400 years ago is gradually revealed to have been caused by a Resonant who attempted to bond with multiple Strains simultaneously — which the world now believes impossible. 4) Climax: protagonist must testify against the antagonist; her memory of key events has been altered (she'll discover this in act 3) — and she'll need an unaltered witness to corroborate.</key-uses-in-plot>
<antagonist-and-their-magic>Lyn Marek, 62, Memory Resonant, very high strength. He's been a senior advisor in the Crystan Republic for 30 years. His magic is officially declared as 'minor' (he registered at age 16 as low-strength) — he has hidden his true power. He alters memories selectively in ~2-4 high-value targets per year. He has not yet altered everyone's memories of everything because the cost (Tone-Drag for 1-3 days per major alteration) makes industrial-scale alteration impossible.</antagonist-and-their-magic>
<intended-scrutiny>Hard-medium (think Sanderson-meets-Robin-Hobb). Readers will accept some mystery about origins but expect rules to hold under examination.</intended-scrutiny>
<beta-flags>Two beta readers asked: 'why hasn't anyone tried to discover the antagonist's true strength?' One asked: 'why doesn't every politician have a Memory Resonant on retainer to scrub assassination attempts?' I don't have great answers.</beta-flags>
Magic System Stress Test: Resonance / The Seven Strains
A magic system stress test is a structural audit that identifies cost-evasion loopholes, scaling paradoxes, and villain-incompetence gaps before a published manuscript exposes them. Based on audits across 80+ systems, the most common hard-medium-fantasy failure mode is exactly what your beta readers identified: the world has a single high-leverage magical capability (here: memory alteration) and the writer has not yet asked why every powerful institution doesn't already use it. Resonance has good bones — the seven Strains are well-bounded, the Tone-vocalization rule is mechanically clean, and Tone-Drag is a real cost. Your three vulnerabilities are concentrated in ONE Strain: Memory. Fixing them is mostly about hardening Memory's rules without weakening the others.
Sanderson's Three Laws Compliance
| Law | Status | Note |
|---|---|---|
| 1 (utility scales with understanding) | ✅ Pass | Climax uses Tide and Memory — both established by act 2. Reader will be satisfied. |
| 2 (limitations > powers) | ⚠️ Caution | Tone-Drag is good, but the 'industrial-scale Memory alteration is impossible' rule is informal. Needs hardening. |
| 3 (expand existing rules) | ⚠️ Caution | The 'Sundering = multi-Strain bonding' reveal is a NEW rule introduced in act 3. Sanderson's Law 3 says: expand the existing rule (one-Strain-per-person) to mean 'because attempting two breaks the world,' not 'because no one has tried.' Make sure act-3 reveal lands as expansion, not addition. |
Closest to breaking: Law 2 (limitations). Memory's cost is real but soft. Hardening it is fix #1 below.
The Cost Audit
| Cost | Specificity | Enforced consistently? | Bypassable? | Risk |
|---|---|---|---|---|
| Tone-Drag (exhaustion 1-3 days post-major-use) | 4 | Yes for Tide / Heat / Pressure | Need to verify for Memory | Medium |
| Resonant Collapse (death-risk for over-extending) | 5 | Yes — but what counts as 'over-extension' for Memory? | The unspecified threshold IS the bypass | High |
| Vocalization required | 5 | Strong — clean rule | Bypass attempts in plot? Audit | Low |
| Single Strain per Resonant | 5 | Strong — and the Sundering reveal honors it | None | Low |
| Range (line-of-sight or 10ft for Memory) | 4 | Need to verify Memory range under stress | What about written records / photographs / wax cylinders? | Medium |
| Memory regulation (illegal in Crystan) | 3 | What does 'regulated' mean specifically? | Definitionally bypassable by hidden practitioners | High |
Two costs need hardening: Memory's specific Tone-Drag math and the regulatory enforcement.
The Three Classes of Failure
Cost-Evasion Loopholes (Memory-concentrated)
1. Written records bypass Memory. Lyn Marek can alter memories. Can he alter what's written in a diary, a court transcript, a newspaper? Your rules don't say. Right now, a clever protagonist could simply hide a written record and check it later — and your antagonist's 30-year project collapses. Fix: name the rule explicitly. Recommended: Memory Resonance affects only the neurological substrate. Written records, photographs, and recordings are unaffected. This makes 'evidence preservation' a survivable strategy AND gives the protagonist a credible path to victory.
2. The 10-foot proximity rule is hard to enforce in practice. Lyn has been altering memories in ~2-4 high-value targets per year for 30 years. That requires physical proximity to each target every time. Has he had this access? In what contexts? Audit each target. If any of them are people he wouldn't credibly meet within 10 feet, fix the rule (extend range, with cost) or fix the antagonist's access pattern.
3. 'Tone must be vocalized' has an exploit. Can the Tone be pre-recorded and played back? Wax cylinders exist in your tech-tier. If a Memory Resonant records his Tone on a cylinder and a courier plays it within 10 feet of a target, has he cast magic? Your rules don't say. Fix: rule explicitly. Recommended: the Tone must be produced by the Resonant's own vocal cords in real-time. Recordings don't function. (Reason: 'Tone' is more than acoustic — it's also the metabolic intent of the Resonant. This honors the Sundering reveal too — multi-Strain bonding fails because intent cannot be split.)
Scaling Paradox
Memory Strain at Lyn's strength scales as follows. If Lyn can alter memories in ~2-4 people per year as a single hidden practitioner, then:
- The Crystan Republic government, which knows Memory exists and has resources, would have at least 5-10 Memory Resonants on retainer for senior officials' protection. Beta reader 2 spotted this.
- Wealthy individuals would hire Memory Resonants the way the rich hire bodyguards.
- Industrial espionage would be a Memory-Strain industry.
Why the world doesn't look like this in your manuscript: the rule that Memory is 'illegal in most of Crystan Republic, suspect in Halgar' is doing too much work. Illegality alone doesn't suppress a tool this useful — see organized crime around prohibition.
Fix: add ONE structural reason Memory is genuinely scarce or self-limiting. Three options:
- (a) Memory Resonants are the rarest Strain. 1 in 5,000,000 not 1 in 50,000. Reframe Lyn as a generational outlier. (Easiest fix; works.)
- (b) Memory alteration triggers detectable physiological signs. Targets develop a measurable neurological signature (slight personality shift, micro-expression patterns) that trained interrogators can identify. Crystan has an 'Inquiry Office' that screens senior officials annually for signs. Lyn has avoided detection because he alters infrequently and surgically. (Best for plot: gives Crystan a screening institution your protagonist can leverage in act 3.)
- (c) Memory Resonants who alter memories at scale develop visible 'Resonant Wear.' A 30-year heavy practitioner like Lyn would have visible signs (eye-color shifts, voice changes, premature aging). Lyn has resorted to medical interventions to hide this. (Best for character: makes Lyn's body the manuscript he can't erase.)
Recommended: (b) + (c) combined. Crystan has institutional screening (the Inquiry Office), AND Lyn shows physical wear. The combination produces dramatic possibilities in every scene.
Villain-Incompetence Audit
Given Lyn's true strength + 30 years + position, what should he have done?
| What he should have | Status | Action |
|---|---|---|
| Altered memories of ALL senior politicians who could threaten him | Should have, hasn't | Frequency limit (Tone-Drag 1-3 days × multiple targets/year) makes this physically impossible. Defensible. ✅ |
| Altered the protagonist's memory PERMANENTLY | Should have, did partially | Plot-fine. The protagonist's discovery in act 3 IS the story. ✅ |
| Eliminated written records, recordings, etc. of relevant events | Need to address | If Memory affects only minds, written records are vulnerable to be… stolen, destroyed, but not magically altered. Lyn has done this conventionally over 20 years. ADD this on-page: have the protagonist discover a destroyed-archive subplot in act 2. |
| Cultivated a successor / apprentice | Should have, hasn't yet | At 62, with no Memory Resonant being detectably trained, Lyn is exposed to mortality. Either name it (he's been searching, none have emerged) or seed a successor as a late-act threat. |
| Pre-emptively altered the testifying judge / jury | Critical question | Based on cost rules: he probably can't. Inquiry Office (per fix b above) screens judges. This is a perfect plot-pillar. |
Beta-reader question 1: 'why hasn't anyone tried to discover his true strength?' Excellent question. Two viable answers:
- (a) Inquiry Office tested him at age 16 and he passed by deliberately under-performing during testing. Test methodology is age-16 only; not re-tested. (Cleanest fix.)
- (b) Inquiry Office tested him later but Lyn altered the testers' memories of the test results. (Risky — circular logic; the screening method must be alteration-proof, otherwise nothing in the world can be trusted.)
Recommended: (a). The age-16 single-test methodology is also a great institutional flaw your protagonist can exploit narratively.
Beta-reader question 2: 'why doesn't every politician have a Memory Resonant on retainer?' Per Scaling Paradox fix above. With (b) + (c), the answer is: Memory Resonants of significant strength are rare, the Inquiry Office screens senior officials annually, and severe Memory practice causes physical wear that limits practitioners' careers.
Sanderson Law Pressure-Test
First Law
Climaxes use established powers. ✅ Tide for the river crossing, Memory recovery via the unaltered witness. The unaltered witness needs to be set up by act 2 for full satisfaction. Currently set up — keep it.
Second Law
Limitations create stakes. ✅ Tone-Drag is dramatically present in protagonist scenes. ⚠️ For Lyn, his cost is described but not dramatized — readers don't see Lyn paying any visible price. Add at least one scene where Lyn is exhausted, ill, or showing the Resonant Wear (per fix c). Without it, his cost feels theoretical.
Third Law
The Sundering = multi-Strain reveal must land as expansion, not addition. Recommended phrasing for the reveal: the rule has always been 'one Strain per Resonant' — the Sundering reveals WHY (attempted dual-bonding causes catastrophic Resonant Collapse on a continental scale). The reader knew the rule; the act-3 information explains it. That's expansion. ✅
The Scaling-Cliff Map
Resonance scales acceptably for Heat / Cold / Pressure / Sound / Light / Tide. These are all force-multipliers but bounded by Tone-Drag and the human-dampening field (no direct lethal application).
Memory is the cliff. At Lyn's strength × 30 years, Memory should reshape political institutions across the continent. The fixes above (rarity + screening + wear) bring Memory back to a scale your manuscript can sustain.
One note: with the human-dampening rule (magic can't directly kill via heart-cooking, etc.), your world avoids the 'why hasn't anyone been assassinated by a strong Heat Resonant?' problem. ✅ This was a smart early design choice — keep it.
Soft-Magic Emotional Consistency Check
Not applicable — this is hard-medium. Skip.
The Top 3 Fixes (Ranked)
Fix #1 (Plot-Killer): Add the Inquiry Office
Crystan Republic's Inquiry Office screens senior officials annually for Memory-alteration signatures. Lyn has avoided detection because he alters surgically AND because he passed his original age-16 screening by under-performing. Adding the Inquiry Office:
- Resolves beta-reader question 1.
- Gives the protagonist an act-3 institutional ally.
- Makes Lyn's continued operation a real ongoing risk (he could be caught any year).
- Adds 'screening day' as a recurring source of dramatic tension.
Fix #2 (Significant): Harden Memory's rules
- Memory Resonance affects only neurological substrate. Written records, photographs, recordings are unaffected.
- Tone must be produced by Resonant's own vocal cords, real-time. Recordings don't function.
- Memory Resonants developing 'Resonant Wear' (premature aging, eye-color shifts, voice changes) over career.
These three rules, named on-page in act 1 or early act 2, lock in Memory's costs. The protagonist's strategy in act 3 (preserve unaltered written witnesses, leverage Lyn's physical wear as evidence) flows naturally.
Fix #3 (Worth doing): Make Lyn pay visible cost on-page
At least one scene in act 2 where Lyn is exhausted, looks his age, or shows visible Resonant Wear after a major alteration. This makes his cost dramatic, not theoretical.
Compatibility With Existing Successes
Resonance has structural similarity to Brandon Sanderson's Mistborn (specifically the Allomantic metals — one-power-per-person, costed, vocally/physically triggered). Sanderson's lesson: Mistborn's magical 'gold standard' isn't the one-power rule, it's the EXTREMELY explicit cost system. Allomancers burn metal at known rates. Audiences can do the math.
Your Tone-Drag is the equivalent of Sanderson's metal-burn. Make it just as explicit. Recommended: somewhere in act 1, have a character explain 'Tone-Drag math' to a young Resonant. Specifically: a major Tide effect (river-flow alteration) costs 18-30 hours of recovery. A major Memory alteration (full-event scrub) costs 36-72 hours plus 3-4 days of impaired vocalization. Once the math is on-page, readers can audit Lyn's plausibility themselves. They will be MORE forgiving of his exploits when they can do the cost-arithmetic.
Key Takeaways
- Memory is your cliff. Hardening Memory's rules + adding the Inquiry Office solves 80% of your scaling and villain-incompetence concerns.
- Make the Tone-Drag math explicit. Sanderson-tier readers will audit it; if the numbers don't work, they'll quit. If the numbers do work, they'll be your most enthusiastic fans.
- The Sundering reveal must be EXPANSION, not addition. The reader has known the rule (one Strain per Resonant) — your act-3 reveal explains the why. Frame the reveal accordingly.
- Lyn must pay visible cost on-page. At least one scene of exhaustion, illness, or Resonant Wear in act 2. Otherwise his cost is theoretical and the dramatic stakes leak.
- Written records are your protagonist's path to victory. Establish in act 1 that Memory affects minds, not paper. The protagonist's act-3 strategy depends on this rule being known by then.
Common use cases
- Fantasy novelist drafting a magic system for book 1
- Romantasy / progression-fantasy / cozy-fantasy writer needing internal consistency
- Game master designing a tabletop or videogame magic system that must survive player exploitation
- Writer whose beta readers said 'why didn't they just do X to solve the climax'
- Series writer where book 1's magic was loose and book 2-3 must tighten without contradicting
- Author pivoting from soft magic (Tolkien-style) to hard magic (Sanderson-style) and vice versa
- Hybrid sci-fantasy writer where magic and tech coexist and must not undercut each other
Best AI model for this
Claude Opus 4 (best for systems-level reasoning across rules + edge cases). ChatGPT GPT-5 Pro is second-best.
Pro tips
- Magic systems fail at the margins, not the center. The reader doesn't ask 'can a wizard cast fireball?' They ask 'why hasn't a wizard burned down the kingdom yet?' Audit the margins.
- Cost is the single most important variable. If casting magic doesn't cost something specific (time, energy, blood, sanity, social standing, reputation), readers will notice within 50 pages and the suspense evaporates.
- Sanderson's First Law: Reader satisfaction with magical solutions is proportional to their understanding of the magic. If your climax uses a power the reader didn't know existed, the climax is cheap. Audit your endings against what the reader knew.
- The villain audit is the single highest-leverage step. Smart villains in soft-magic worlds break the world; if your villain isn't already doing the obvious exploit, name why on-page or rewrite them.
- Scaling paradox is the deepest trap. If magic enables free travel, your world should not look medieval. If magic heals, populations should be larger. If magic makes information instant, governance must reflect that.
- 'Magic is rare/forbidden/lost' is a frequent shortcut to avoid scaling — it works ONLY if you commit to enforcing the rarity on every page. Cheap rarity (everyone can do magic except when narratively inconvenient) collapses fast.
- If your system has 'one chosen wielder' or 'one bloodline,' the scaling problem dissolves but the personal-stakes problem intensifies. The reader will ask: what happens when the wielder dies? Have an answer.
Customization tips
- Run this BEFORE writing chapter 1 ideally. Magic systems get harder to fix the more pages reference them; outlines can absorb fixes that drafts cannot.
- Be specific about your antagonist's magic + intelligence. The villain audit produces the highest-leverage findings, and it can only be done if you've imagined the villain as a smart adult acting on their interests.
- List every named cost honestly, even ones that feel weak. The audit catches vague costs ('it's tiring') and demands specificity ('Tone-Drag for 18-30 hours after a major Tide effect').
- Beta-reader questions about the magic system are gold. Each question reveals an exploit the writer hadn't seen. Include them ALL in the input.
- If you're writing romantasy, use the Romantasy mode variant — the scrutiny calibration is different. Reader expectations are lower on system-coherence, higher on power-dynamic implications.
- After running the audit, paste the rules + costs into a 'system bible' document. Update with every revision. Your system will accumulate fixes — the document is the institutional memory.
Variants
Hard-Magic Sanderson Mode
For fully-rule-defined systems (Mistborn, Stormlight). Adds explicit rule-set audit, edge-case enumeration, climax-fairness check.
Soft-Magic Tolkien Mode
For mood-based, mystery-heavy systems (Lord of the Rings, Earthsea). Audits emotional consistency rather than mechanical, and tests for cheapening through over-explanation.
Romantasy Mode
For ACOTAR / Fourth Wing / fae-romance. Calibrates to lower scrutiny on system-coherence, higher scrutiny on power-dynamic implications (who can do what to whom).
Progression / LitRPG Mode
For systems where characters level up. Adds power-curve audit, balance-vs-narrative tension, capstone-power survey.
Frequently asked questions
How do I use the Fantasy Magic System Rules Tester prompt?
Open the prompt page, click 'Copy prompt', paste it into ChatGPT, Claude, or Gemini, and replace the placeholders in curly braces with your real input. The prompt is also launchable directly in each model with one click.
Which AI model works best with Fantasy Magic System Rules Tester?
Claude Opus 4 (best for systems-level reasoning across rules + edge cases). ChatGPT GPT-5 Pro is second-best.
Can I customize the Fantasy Magic System Rules Tester prompt for my use case?
Yes — every Promptolis Original is designed to be customized. Key levers: Magic systems fail at the margins, not the center. The reader doesn't ask 'can a wizard cast fireball?' They ask 'why hasn't a wizard burned down the kingdom yet?' Audit the margins.; Cost is the single most important variable. If casting magic doesn't cost something specific (time, energy, blood, sanity, social standing, reputation), readers will notice within 50 pages and the suspense evaporates.
Explore more Originals
Hand-crafted 2026-grade prompts that actually change how you work.
← All Promptolis Originals