Tabletop RPG Reference for Dice Odds, Bestiary and Character Creation

Almost every argument that stalls a session is a question with an answer nobody has to hand. What are the tabletop rpg dice odds on this roll. Is that creature actually a fair fight. Did we agree ability scores were rolled or bought. None of these are hard questions. They are just questions the rulebook buried four chapters apart.

This is a tabletop rpg reference written for the middle of a session rather than the week before one. Every page in the tabletop rpg reference opens with the figures, explains them underneath, and says plainly where a rule stops being general and starts belonging to one system.

What this tabletop rpg reference covers

• Dice probability

  exact figures

  Why a d20 is a flat line and 3d6 is a bell, what advantage is worth at each target number, and how to build a chart for a mechanic the books do not cover.

• Bestiary

  creature reference

  How to read a stat block from the bottom up, what challenge rating actually measures, where it misleads, and which free creature collections are worth keeping.

• Character creation

  step by step

  Concept before numbers, the three ways to set ability scores and what each says about a campaign, and a backstory a referee can actually use.

• Systems

  comparison

  What the major families do differently, from d20 rolls to dice pools, percentile skills and playbooks, and how to tell which one suits a group before buying it.

• Glossary

  terms

  The vocabulary that appears in every rulebook without ever being defined: action economy, session zero, failing forward, the fiction.

Dice odds, and why shape beats average

A twenty-sided die has no middle, which is most of why D&D 5e and Pathfinder 2e feel the way they do. Each face turns up 5% of the time, so every point of target number is worth exactly five percentage points, all the way up the scale. Sum three six-sided dice instead, the way GURPS does, and the line collapses into a bell: ten and eleven appear 12.5% of the time each, three and eighteen once in 216 rolls.

Both average 10.5. They feel nothing alike, which is the whole argument for looking at distributions rather than means. The tabletop rpg dice odds pages work each of these out exactly and show what rolling twice is worth at every target, which turns out to range from about one percentage point to twenty-five.

The practical consequence shows up in how a referee sets difficulty. On a flat die, raising a target by two costs every character the same ten percentage points, so difficulty can be tuned by arithmetic. On a curve it cannot: the same two points might cost a middling character twenty points and an expert three. Referees who move between the two families and keep the same instincts about "a bit harder" get it wrong in one direction consistently.

The bestiary, and what a difficulty rating knows

A creature entry is a working document: nine or ten numbers a referee can read and run immediately. The difficulty rating attached to it compresses how much punishment the thing absorbs and how much it deals into a single figure, calibrated against an assumed party.

That figure is useful and routinely over-trusted, because it knows nothing about terrain, magic items or whether the party can simply fly out of reach. The fantasy rpg bestiary section covers how entries are built and compared, and points at the collections that cost nothing. A free fantasy rpg bestiary will carry most of a campaign before anything has to be written from scratch.

Character creation without the rewrite

Most rulebooks present character creation in the order that suits the printer, and the result is a completed sheet that nobody can play. Working the other way round produces fewer rewrites and better characters: first a sentence describing what the character does when a plan fails, then the numbers that support it.

The character creation pages cover the three standard ways of setting ability scores and what each one says about the campaign, along with the part most guides skip: what a group should agree before anyone rolls anything.

How these pages are written

Numbers here are computed rather than remembered. Dice distributions are enumerated as exact rational values and rounded only when they are printed, so a figure quoted on one page matches the same figure on another. Where something is a judgement call rather than arithmetic, it is written as one.

Where a claim belongs to a specific game, the game is named. Where it applies to the underlying mechanic regardless of publisher, it is left general. That distinction matters more than it sounds: a great deal of received table wisdom is one system's quirk repeated until it sounded like a law, and a tabletop rpg reference that blurs the two is worse than no reference at all.

Common questions