Part Two: The Rules
Chapter Eighteen: The Basics
Part Two: The Rules
"Every Sentinel who has survived something they shouldn't have will tell you the same thing. Preparation is the weapon you bring to the dark. Chaos is the moment itself. Your survival depends on learning to master both."
T he d20+ is a unified system. The same mechanic that resolves a Goblin Shaman reading the Ley Line frequencies beneath a city also resolves a Fae Witch putting a Demon through a brick wall. Learn it here, and you can play anything the world throws at you.
The Roll
When a Persona attempts something difficult, something where failure carries a cost, the Conductor calls for a check. Every check in the game uses the exact same formula:
Score = d20 + Skill Score + Augment Dice
You roll the twenty-sided die. You add your fixed Skill Score. You add any Augment Dice you have earned the right to roll. Finally, you compare the total to a Target Number or an opponent's defense.
The result tells you not just whether you succeeded, but by how much. In d20+, the margin between success and failure is where the fun begins.
The Three Traits
Every Persona is built upon three fundamental forces. They define who you are, what you can endure, and what you are capable of when the moment counts.
MIND: Intellect, strategic processing, memory, and the capacity to understand complex systems. A high-Mind Persona sees the pattern before anyone else in the room realizes there is a puzzle. Their derived Skills are Knowledge and Logic.
BODY: Physical power, speed, coordination, and raw endurance. A high-Body Persona is the one you want in front of you when the door breaks open. Their derived Skills are Might and Grace.
SPIRIT: Willpower, perception, social gravity, and the frequency sensitivity that connects a being to the world around them. A high-Spirit Persona feels things others miss and bends rooms toward their intent. Their derived Skills are Will and Sense.
Traits scale from 1 to 12. A score of 3 is capable. A score of 8 is exceptional. A score of 12 is the province of those who have spent a lifetime sacrificing everything else for a single axis of mastery.
The Death Spiral: Traits are also your wound tracks. When you take damage, the relevant Trait drops. As a Trait falls, every Skill tethered to it falls with it. A Persona with a Body of 5 who takes 3 wounds now rolls as if their Body were 2.
The Six Skills
Skills represent your developed aptitude within a specific Trait domain.
Your Skill Score is a combination of your innate Trait and your trained expertise. At the table, you do not add your Trait and your Skill separately. You simply add them together on your character sheet to create a single, unified number.
Skill Score = Trait Score + Species Bonus + Origin Bonus + Story Point Investment
Trait Score is the foundation. Your Body score is the baseline for both Might and Grace. Your Mind score anchors Knowledge and Logic. Your Spirit score drives Will and Sense. Raising a Trait lifts both Skills derived from it. Every Persona begins character creation with all three Traits and all six Skills at 1, before any bonuses are applied. (See Chapter Thirteen for the full build order.)
Species Bonus comes from your ancestry. Each species carries inherited aptitude in specific Skills. A Hobgoblin's six thousand years of underground warfare shows in their Might and Will before they train a single day. Species bonuses are fixed at character creation.
Origin Bonus comes from your background and grants additional bonuses to the Skills that shaped your life. Origin is chosen during character creation.
Story Point Investment is how Skills grow through play. You can spend Story Points to increase any Skill directly. The cost scales with the target level you are reaching: target level × 2 Story Points. Raising a Skill from 4 to 5 costs 10 SP. Raising it from 7 to 8 costs 16 SP. Specialization deepens, but it compounds in cost.
A Goblin with Spirit 3, a +2 Species Sense bonus, and a +1 Origin Sense bonus rolls d20 + 6 for any Sense check. This is all calculated once to provide a single Skill Score to add to your d20 roll.
| Skill | Trait | What It Covers |
|---|---|---|
| Knowledge | Mind | History, lore, identification, languages, arcane theory |
| Logic | Mind | Tactics, problem-solving, mechanisms, Wonder Gear, patterns |
| Might | Body | Physical force, melee attacks, feats of strength |
| Grace | Body | Speed, finesse attacks, stealth, ranged combat, agility |
| Will | Spirit | Focus, mental resistance, commanding presence, spellcasting |
| Sense | Spirit | Perception, intuition, reading people, detecting frequencies |
Target Numbers (Tn)
When you act against a static obstacle, whether a biometric vault, a sheer cliff face, or a tense negotiation with an unyielding official, the Conductor sets a Target Number based on the unforgiving nature of the task.
| TN | Challenge | Description |
|---|---|---|
| 15 | Basic | A routine task under pressure |
| 20 | Skilled | Requires genuine training or deep focus |
| 25 | Expert | Most people would fail this outright |
| 30 | Master | The absolute limit of a specialist under fire |
| 35 | Legendary | Remembered by those who witness it |
| 40 | Mythical | The stuff of stories told decades later |
Meet or exceed the TN, and you succeed. Beat the TN by 10 or more, and something extraordinary happens. The rules for Mounting Success are detailed in Chapter Nineteen.
Augmentation Dice
This is the "Plus" in the d20+.
Beyond your flat Skill Score, you build a dynamic pool of additional dice ranging from d4 to d12. These are your Augment Dice. They represent the compounding advantages of lethal preparation, masterwork equipment, magical assistance, and superior positioning. You roll these dice alongside your d20 and add the total.
There are five types of Augment Dice:
| Type | Source |
|---|---|
| Gear | Equipment quality (weapons, armor, tools) |
| Training | Profession Trainings (practiced expertise and technique) |
| Magic | Active spells, enchanted items, and Wonder Gear |
| Tactic (TAD) | Positional advantages earned through Setup Actions |
| Special | Rare abilities, faction benefits, and unique circumstances |
Most Trainings grant a Training die. A few exotic Trainings grant a Tactical, Special, or Magic die instead; the Training’s description says which.
Two absolute rules govern this pool:
1. One die per type. You may roll a maximum of five Augment Dice on any check. If you have multiple sources providing a Training die, you do not roll both. You take the largest die and leave the lesser one behind.
2. The Trait Cap. The total number of Augment Dice you can roll cannot exceed your current Trait score for that check. A Persona whose Body has been reduced to 2 can roll a maximum of two Augment Dice on a Might or Grace check, even if they possess all five types.
Training Aug Dice begin at d4 when first acquired. Every subsequent Story Point investment upgrades the die one step (d4 → d6 → d8 → d10 → d12). A veteran's d12 Training die is the mechanical expression of years spent bleeding for a craft.
The art of the game lives in this pool. Reading the moment, choosing which dice to bring, and knowing how to relentlessly stack your advantages is the difference between surviving an encounter and dominating it.
The Critical
On a natural 20, you add a flat 10 to your d20 result. This makes the effective d20 component a 30.
Against most opposition, a base score of 30 lands you deep into Mounting Success territory, triggering devastating secondary effects. But against a highly prepared, heavily augmented defender, even a 30 can be blocked. That tension is entirely the point.
The Short Version
Roll the d20. Add your fixed Skill Score. Add whatever Augment Dice you have earned the right to throw. Compare it to a Target Number or an opponent's defense. Beat it to succeed. Beat it by 10 or more to do something more memorable. The art is through clever execution to ensure you always have as many Augment Dice as possible.
That is the entire game. Everything in the next chapter is an elaboration of that single premise.