Your World Has Rules. Now Your Tools Can Compute Them.
A rules engine for fiction. Define stats, write formulas with dice notation, run probability analysis, and ensure your magic system actually works. Not just for TTRPGs — for any fiction with structured rules.
Brandon Sanderson's Allomancy has precise rules about what each metal does and how they interact. Robert Jordan's One Power has defined limits on strength, linking, and burnout. Your world has rules too — maybe a magic system, a technology framework, a power hierarchy, or combat mechanics. Ishvana lets you define those rules and compute with them.
Name your power tiers. Abilities reference these by number.
Organize stats and formulas into groups (e.g., Physical, Mental, Social). These are separate from Wings.
Pre-seeded math-bound options for your abilities. You can add, remove, or rename options to match your system.
Define your system's vocabulary — elements, traditions, components, or any other category your abilities need.
Probability Analysis
Stop guessing whether your system is balanced. Compute it.
Pool Analysis
Roll any dice pool and see the full probability distribution. "What are the odds of rolling 3 successes on 5d10 target 7?" Ishvana computes it instantly.
Opposed Rolls
Simulate contested checks between two entities. Compare probability curves to see who wins — and by how much — across thousands of simulated outcomes.
Power Curves
Plot how a character or ability scales across levels or stat ranges. See breakpoints, diminishing returns, and balance issues in your progression systems.
DC Tier Analysis
Define difficulty tiers (Easy, Medium, Hard, Impossible) and see what percentage of your characters can meet each threshold at any given point in the story.
Preset Systems
Start from a proven foundation or build entirely from scratch.
| System | What It Includes |
|---|---|
| D&D 5e | Six ability scores, proficiency bonus, AC calculation, saving throws, skill checks, spell slot progression |
| Pathfinder 2e | Four-tier proficiency, three-action economy, MAP penalties, DC adjustments by level |
| Fate Core | Fate ladder (-2 to +8), aspects, stress tracks, consequence slots, skill approaches |
Rules Lawyer AI
The Rules Lawyer reads your Legendry entries and checks them against your defined mechanics.
Stat Validation
Checks that character stat blocks are internally consistent. If your system caps STR at 20 and a character has 23, the Rules Lawyer flags it.
Formula Consistency
Validates that damage formulas, skill checks, and ability calculations produce reasonable results across your cast. Catches the wizard who accidentally does more melee damage than the fighter.
Rule Conflict Detection
Identifies when two rules in your system contradict each other. 'Fire immunity' on a character who also has 'takes double fire damage' — the Rules Lawyer catches the conflict.