Dice Roll
General Principle
All actions, whether physical, arcanotechnological, or social, use the same roll mechanic:
d20 + modifiers >= Difficulty Class (DC)
- d20: the 20-sided die represents the chance factor.
- Modifiers: bonuses from characteristics, skills, affinities, or equipment.
- DC: threshold set by the GM based on the action’s difficulty.
This unified system applies to everything: attack, skill, saving throw, perception, etc.
Difficulty Class (DC) Table
Standard DC (for characters with total modifiers of +10 to +25)
| Difficulty | DC | Description | Example Task |
|---|---|---|---|
| Trivial | 10 | Failure only on extreme bad luck | Walking on flat ground |
| Very Easy | 15 | Routine for a professional | Climbing a ladder |
| Easy | 20 | Requires a minimum of effort | Picking a simple lock |
| Medium | 25 | Requires skill AND concentration | Disarming a standard trap |
| Hard | 30 | Challenging even for an expert | Hacking a secured system |
| Very Hard | 35 | Limit of human capabilities | Climbing a smooth wall in the rain |
| Heroic | 40 | A memorable feat | Convincing a sworn enemy to help you |
| Legendary | 45 | Nearly impossible | Forcing open an adamantium door |
| Mythic | 50 | Beyond human ability | Resisting the will of a god |
Suggested Contextual Modifiers
| Condition | DC Modifier |
|---|---|
| Inadequate tools | +5 |
| Unfavorable conditions | +5 to +10 |
| Under time pressure | +5 |
| Injured or fatigued | +5 to +10 |
| Help from a competent ally | -5 |
| Superior quality tools | -5 |
| Thorough preparation | -5 to -10 |
Design Note: This scale assumes that experienced characters have total modifiers between +15 and +30. Beginning characters (modifiers +5 to +15) should primarily face DCs of 15-25.
Roll Calculation
Final Result = d20 + Characteristic + Skill + Contextual Modifiers
Examples:
- Forcing a door -> d20 + Strength + Skill (Athletics)
- Convincing a guard -> d20 + Charisma + Skill (Persuasion)
- Casting a complex spell -> d20 + Intelligence + Arcanotechnological Affinity
Power Level Guide
To adapt challenges to character level, consider their total modifiers:
| Character Level | Typical Modifiers | Recommended DCs | Description |
|---|---|---|---|
| Novice | +5 to +10 | 10-20 | Beginning the adventure |
| Apprentice | +10 to +15 | 15-25 | A few missions completed |
| Competent | +15 to +20 | 20-30 | Established professional |
| Expert | +20 to +25 | 25-35 | Recognized master |
| Master | +25 to +30 | 30-40 | Living legend |
| Legendary | +30 to +35 | 35-45 | Beyond human |
GM Advice: A “medium” challenge should have roughly a 60% chance of success. Adjust based on the desired tone:
- Heroic: DC = Total Modifier + 5 (75% success)
- Realistic: DC = Total Modifier + 10 (50% success)
- Brutal: DC = Total Modifier + 15 (25% success)
Critical Successes and Failures
-
Natural 20 (before adding bonuses) -> Critical success
- The action succeeds beyond expectations.
- The GM may grant an additional effect (perfect success, tactical advantage, spectacular result).
-
Natural 1 (before adding bonuses) -> Critical failure
- The action fails, often catastrophically.
- May result in a counter-effect, equipment loss, or an unfavorable situation.
Criticals are not modified: a 20 remains a total success, even if the total is below the DC. Conversely, a 1 remains a total failure, even if the final result exceeds the DC.
Opposed Rolls
When an action is directly opposed to another character’s action (e.g., duel, grapple, concealment, persuasion vs. deception):
- In case of a tie, the advantage goes to the defender (or the one maintaining the initial state).
Examples:
- Picking a lock while someone tries to block it.
- Convincing an NPC while another contradicts them.
- Physically wrestling against an opponent.
Advantage and Disadvantage
Certain conditions grant an advantage or a disadvantage:
- Advantage -> roll 2d20 and keep the higher result.
- Disadvantage -> roll 2d20 and keep the lower result.
These effects do not stack: multiple advantages or disadvantages make no difference, unless the GM specifies otherwise.
Examples:
- Having time, good conditions, or assistance -> Advantage.
- Being injured, rushed, or in darkness -> Disadvantage.
Saving Throws
Saving throws allow a character to avoid a harmful effect: trap, spell, explosion, poison, etc.
Saving throw = d20 + characteristic modifier >= DC of the effect
- Each effect has a saving throw DC defined by its source (e.g., spell, trap, creature).
- The GM announces the relevant characteristic (Strength, Dexterity, Constitution, etc.).
Examples:
- Resisting a spell -> d20 + Intelligence
- Dodging an explosion -> d20 + Dexterity
- Enduring pain -> d20 + Constitution
Contextual Modifiers
The GM may apply bonuses or penalties based on the situation:
| Condition | Typical Effect |
|---|---|
| Slippery terrain | -2 to DEX roll |
| Appropriate tool | +2 to skill roll |
| Encumbrance | -1 to all physical rolls |
| Ally’s help | +2 (or advantage, depending on the case) |
| Fatigue or injury | disadvantage on the affected actions |
System Philosophy
One principle for everything: roll 1d20, add the right modifiers, beat the DC. Simplicity ensures smooth gameplay, but characteristic and context choices retain their full weight.
This system emphasizes:
- consistency (same rules for all cases),
- speed (resolution in a single roll),
- and flexibility (the GM adjusts the DC, not the formulas).