🛡️ One Hero Engine – Core Rulebook (v 0.12)

A solo-focused, narrative-driven RPG for mythic storytelling, bold decisions, and immersive worldbuilding. Designed to be lightweight in mechanics and rich in expression, One Hero Engine puts the story in your hands—no game master required.

Part I: Creating Your Hero

1. What Is One Hero Engine?

One Hero Engine (OHE) is a solo tabletop roleplaying system where you take the role of a single hero facing challenges, enemies, and unknown fates in a dynamic, mythic world.

Key Points:

• No game master required
• Oracle tools resolve uncertainty
• Lightweight but expressive mechanics
• Milestone-based leveling
• Character-first design

Quick Reference:

• Solo RPG: Your hero, your adventure.
• Tools: Oracle and narrative twists.
• Progression: Milestone and levels guide growth.

Character Sheet

2. Character Creation Overview

1. Assign Stats: Use 14, 13, 12, 11, 11, 11. You may redistribute up to 2 points between any scores.
2. Choose a Race: Provides +1 to any stat, a saving throw specialization, and 1 of 5 racial Traits.
3. Choose a Class: Grants a saving throw specialization and 1 of 5 class Traits.
4. Pick 3 Tags: Narrative keywords that describe your background and skills.
5. Choose a Casting Path (optional): For spellcasting, refer to Section 14.
6. Finalize Derived Stats: Calculate stat bonuses, Soak, MP (if applicable), and record traits and tags.

Quick Reference:

• Steps: Assign → Race → Class → Tags → Casting Path → Finalize.
• Customization: Flexible stat allocation and tag selection.

3. Ability Scores & Saving Throws

Stats

Modifier Formula: (Stat - 10) ÷ 2, rounded down

Combat Statistics

• Armor Class (AC): Your default AC is 9 plus your Dexterity modifier.
• To-Hit Bonus: When making attack rolls, use the higher of your Strength or Dexterity modifier.
• Damage Bonus: For melee attacks, add your Strength modifier; for ranged attacks, add your Dexterity modifier.

Quick Reference:

• AC: 9 + Dex modifier.
• To-Hit: Best of STR or DEX modifier.
• Damage: STR for melee; DEX for ranged.

Saving Throws

• Roll: 1d20 + modifier.
• Advantage: Apply if specialized.
• Disadvantage: Apply when enemies have traits or abilities imposing it.
• Spell Save TN: Equal to caster’s full stat score (e.g., INT 15 → TN 15).
• Use the GM or scenario to set difficulty for non-spell saving throws.

Quick Reference:

• Roll: d20 + modifier.
• Bonus: Advantage if specialized.
• Target Number: Caster’s stat for spell saves.

Skill Checks

Skill checks use a roll-under mechanic:

• Roll: 1d20; if the result is equal to or lower than your relevant stat (or stat + bonus/penalty), you succeed.
• Apply Advantage/Disadvantage where relevant:
  • Advantage: Roll two d20s and take the lower result (since lower is better).
  • Disadvantage: Roll two d20s and take the higher result.

Important: Non-skill rolls (attacks, saves, etc.) use a “roll-over” system (d20 + bonus vs. Target Number). Always verify which system applies before rolling.

Quick Reference:

• Skill Check: Roll-under your stat.
• Advantage/Disadvantage: Lower result benefits; higher result hinders.

4. Races

Each race provides:

• +1 to any stat
• 1 saving throw specialization
• Choose 1 Trait from 5 options

Dwarf

Save Specialization: CON

• Stubborn Resilience: Soak +1 vs. physical damage.
• Stonecunning: Ability to sense structural weaknesses.
• Ale-Born Fortitude: Heal 1 HP (once per day).
• Iron Grip: Gain Advantage to resist disarm attempts.
• Cave Whisperer: Effectively detect tunnels or communicate with stone.

Dragonborn

Save Specialization: CHA

• Breath Weapon: Execute a 1d6 cone attack (usable once per session).
• Scaleblessed: Benefit from a natural AC of 13.
• Commanding Roar: Force enemies to test their Morale.
• Elemental Resistance: Gain Soak +1 vs. a chosen element.
• Draconic Tongue: Communicate with draconic creatures and gain cultural insights.

Elf

Subraces:

Dark Elf (Drow)

Save Specialization: INT or CHA

• Shadow Meld: Advantage on stealth checks in darkness or dim light.
• Night’s Edge: Bonus to illusion and mind-affecting spells (usable once per scene).
• Twilight Veil: Enhanced perception in low-light conditions.
• Umbral Insight: Detect hidden details by gaining insights from the shadows.
• Night Stalker: Increased speed and agility when moving through darkness.

Gold Elf

Save Specialization: DEX or INT

• Sunlit Grace: Advantage on skill checks in bright light conditions.
• Radiant Memory: Once per session, recall ancient lore for a bonus on Arcane rolls.
• Golden Resolve: Bonus on Will saves during daylight.
• Dawn’s Favor: Increase initiative by +1 in outdoor, sunlit environments.
• Luminous Step: Temporary movement bonus in bright conditions (usable once per scene).

Wood Elf

Save Specialization: DEX or WIS

• Forest’s Whisper: Advantage on stealth and perception checks in natural terrain.
• Rapid Step: Move silently and quickly through wooded areas (usable once per scene).
• Leafbound Reflexes: Bonus to DEX saves in forested settings.
• Natural Camouflage: Improved ability to hide in natural surroundings.
• Sylvan Empathy: Communicate with woodland creatures for situational advantages.

Halfling

Save Specialization: DEX

• Lucky Dodge: Convert a hit into a miss (usable once per session).
• Quiet Step: Gain Advantage on stealth checks in natural terrain.
• Comfort Seeker: Meals restore +1 HP.
• Hearthborn Heart: Immune to magical fear effects.
• Quick Fixer: Instantly repair small items or disable traps.

Human

Save Specialization: Any

• Versatile Soul: +1 to any stat (applied again).
• Resilient Lineage: Advantage on 1 save per session.
• Adaptable Mind: Advantage on 1 Oracle roll per session.
• Quick Study: Learn a Tag mid-session (1/session).
• Skilled: Start with 1 extra Tag.

Tiefling

Save Specialization: CHA or INT

• Hellfire Touch: Deal an extra +1 fire damage in melee combat.
• Eyes of the Abyss: Detect lies or magical effects (usable once per session).
• Shadowmeld: Gain Advantage on stealth checks in darkness.
• Sin Whisper: Learn an enemy’s secret desire (usable once per session).
• Infernal Will: When using Oracle rolls with dark forces, gain Advantage.

Quick Reference:

• Race Benefits: +1 stat, saving throw specialization, and 1 Trait (choose from 5 options).
• Example: Human offers flexibility and extra tags.

5. Classes & Paths

Each class provides:

• 1 saving throw specialization.
• 1 Class Trait chosen from 5 options.

Select the path that best matches your desired play style.

Fighter Paths

Fighters excel in physical combat. Choose from the following specialized paths (listed alphabetically):

Knight

Save Specialization: STR or CON

• Shield Valor: Gain +1 AC when adjacent to an ally.
• Chivalric Stand: Once per combat, negate an attack that would reduce you below 50% HP.
• Honorable Strike: Deal bonus damage against foes attacking dishonorably.
• Battle Focus: Gain Advantage on Strength-based attacks when standing firm.
• Resolute Guard: Once per day, prevent a critical hit against you or an adjacent ally.

Martial Artist

Save Specialization: STR or DEX

• Precision Strike: When attacking with Advantage, add an extra damage step (according to the Step Dice system).
• Technical Mastery: Your focused strikes bypass part of enemy defenses, ignoring the first step of their damage reduction.
• Counter Expertise: Successfully parrying an attack grants an immediate counterattack with Advantage.
• Grapple Specialist: Efficiently clinch and restrain foes, limiting their ability to counterattack.
• Battle Instinct: In critical moments, gain Advantage on your next unarmed attack, reflecting heightened awareness.

Monk

Save Specialization: DEX or WIS

• Inner Flow: Recover a small amount of MP upon a successful unarmed strike (using standard MP recovery).
• Inner Serenity: Restore modest HP or MP during a short rest through focused meditation.
• Flurry of Blows: Once per combat, unleash a rapid sequence of unarmed strikes, granting one extra attack on your turn.
• Spirit Shield: Generate a transient aura that absorbs part of incoming damage for a brief period.
• Transcendent Focus: Once per session, reroll a failed unarmed attack or skill check.

Paladin

Save Specialization: STR or CHA

• Divine Smite: Once per combat, add extra radiant damage (Step 3) on a successful melee hit.
• Aura of Faith: Grant nearby allies a bonus to saving throws (usable once per session).
• Sacred Protection: When an ally falls, gain temporary HP equal to your level.
• Holy Rally: Restore a small amount of HP to yourself or an ally after a powerful strike.
• Divine Judgment: Once per day, force an enemy to re-roll a failed saving throw.

Ranger

Save Specialization: DEX or WIS

• Precise Shot: Gain Advantage on ranged attack rolls in natural terrain.
• Stealthy Pursuit: Move undetected in forests and rugged landscapes.
• Hunter’s Mark: Mark a foe to increase the damage dealt on subsequent attacks.
• Quick Reflexes: Gain a bonus to Dexterity saves when facing multiple foes.
• Nature’s Insight: Once per scene, use environmental factors to gain a tactical edge.

Swordmaster

Save Specialization: STR or DEX

• Precision Cut: Increase your chance for critical hits on well-aimed strikes.
• Parry and Riposte: When you successfully parry an attack, immediately counter with a bonus attack.
• Flourishing Strike: Execute combo attacks that add extra damage.
• Blade Dance: Temporarily boost your mobility and attack speed during combat.
• Edge of Perfection: Once per combat, reroll a failed attack roll for a decisive strike.

Magic User Paths

Magic Users channel arcane energies. Choose from the following paths (listed alphabetically):

Cleric

Save Specialization: WIS or CHA

• Divine Intervention: Once per session, negate an incoming attack entirely.
• Holy Light: Enhance the healing power of your restorative spells.
• Sacred Ward: Grant temporary damage resistance to yourself or an ally.
• Blessing of Faith: Improve saving throws for nearby allies for a brief period.
• Righteous Fury: Add extra radiant damage to your offensive spells.

Necromancer

Save Specialization: INT or CHA

• Enhanced Raise Dead: Improve your summoned undead minions’ strength or durability.
• Life Drain: Heal yourself in proportion to the damage inflicted by your necromantic spells.
• Deathly Aura: Emit a necrotic aura that deals minor damage over time to nearby enemies.
• Bone Barrier: Conjure a temporary shield of skeletal fragments.
• Soul Channel: Convert the life force of defeated foes into bonus MP.

Sorcerer

Save Specialization: INT, WIS, or CHA

• Wild Surge: Spend an extra 1 MP to increase a spell’s damage by one Step.
• Elemental Affinity: Gain bonus damage when casting spells of your chosen element.
• Magical Flow: Reduce the MP cost for consecutive spells during combat.
• Chaos Bolt: Cast a variable-damage bolt with a chance for additional effects.
• Innate Spark: Recover a small portion of MP when your spell successfully lands.

Warlock

Save Specialization: INT or CHA

• Pact Empowerment: Regain a small MP bonus after each successful spell cast.
• Eldritch Blast: Enhance your signature ranged spell with extra damage.
• Dark Bargain: Once per session, sacrifice a small amount of HP to amplify a spell’s effect.
• Cursed Invocation: Inflict a minor debuff on enemies following a successful spell attack.
• Pact Resilience: Gain a temporary MP shield when critically wounded.

Wizard

Save Specialization: INT, WIS, or CHA

• Arcane Mastery: Lower the MP cost of one spell per session.
• Spell Recall: Once per session, recover a recently cast spell at no additional cost.
• Mystic Archive: Gain bonus effects when recalling arcane knowledge during combat.
• Ritual Casting: Cast designated spells without spending MP when time permits.
• Focused Study: Temporarily boost your casting stat for a particularly challenging spell.

Rogue Paths

Rogues specialize in stealth, subterfuge, and precision. Choose from the following paths (listed alphabetically):

Assassin

Save Specialization: DEX or CHA

• Lethal Precision: Increase your critical hit chance on ambush attacks.
• Silent Takedown: Execute enemies quietly, minimizing detection.
• Poison Mastery: Apply toxins to your strikes that deal damage over time.
• Quick Execution: Burst forward to close gaps rapidly for a surprise strike.
• Death Mark: Once per combat, mark a target to increase damage dealt against it.

Spy

Save Specialization: DEX

• Urban Camouflage: Excel at blending into crowded urban environments.
• Eavesdrop: Gather crucial clues about enemy tactics through careful observation.
• Covert Entrance: Move undetected when infiltrating secure locations.
• Silent Footsteps: Reduce noise to maintain stealth in cityscapes.
• Shadow Intel: Acquire actionable information that provides tactical advantages.

Thief

Save Specialization: DEX

• Agile Fingers: Enhanced ability to pick locks and disarm traps with ease.
• Quick Escape: Increase movement speed for rapid retreats when in danger.
• Opportunist: Gain bonus damage when catching enemies off-guard.
• Sleight of Hand: Improve success rates for pickpocketing or subtle manipulations.
• Evasive Maneuver: Gain a temporary bonus to AC when making a swift escape.

Quick Reference for Classes & Paths:

• Fighter: Knight, Martial Artist, Monk, Paladin, Ranger, Swordmaster.
• Magic User: Cleric, Necromancer, Sorcerer, Warlock, Wizard.
• Rogue: Assassin, Spy, Thief.

Each path provides exactly five unique traits along with a designated saving throw specialization, ensuring that your character’s abilities are both flexible and distinct.

6. Tags & Traits

• Tags: Narrative keywords that describe your hero’s background and skills. They grant Advantage on appropriate rolls (whether using the roll-under or roll-over system).
• Traits: Specific bonuses or abilities from your race, class, or progression. They can affect combat, magic, or narrative events.

Quick Reference:

• Tags: Use for narrative flair and situational bonuses.
• Traits: Permanent bonuses or abilities that grow with your character.

7. Advancement & Leveling

Quick Reference:

• Progression: Incremental stat increases and periodic Trait gains.
• Capstone: Final transformation at Level 10.

Part II: Playing the Game

8. Core Mechanics

All non-skill rolls (attacks, saves, etc.) use a “roll-over” approach: roll d20 + bonus vs. a Target Number. Skill checks, however, use a “roll-under” system.

Advantage & Disadvantage:

• Advantage: Roll 2d20; for roll-over tasks, take the higher; for roll-under tasks, take the lower.
• Disadvantage: Roll 2d20; for roll-over tasks, take the lower; for roll-under tasks, take the higher.

Quick Reference:

• Roll-Over System: d20 + bonus vs. TN.
• Roll-Under System: Roll below stat.
• Adv/Disadv: Adjust dice selection accordingly.

9. Turn Structure

1. Start of Turn: Apply Fray and resolve ongoing effects.
2. Actions (2): Options include moving, attacking, casting, interacting, etc.
3. Use 1 Trait: Activate a trait if desired.
4. Resolve Rolls: Perform all necessary dice rolls.
5. Narrate Results: Describe the action outcomes.
6. Enemy Turn or Oracle Twist: Advance the encounter or invoke Oracle twists.

Quick Reference:

• Phases: Start → Actions → Trait → Rolls → Narration → Resolution.

10. Combat & Fray Dice

• Fray: Represents automatic damage dealt to lower-HD foes.
• Damage Dice:
  • Levels 1–5: 1d6
  • Levels 6–10: 1d8
• Overflow: Excess Fray damage moves to another enemy with equal or lower AC.

Quick Reference:

• Fray Damage: Automatic damage; increases with level.
• Overflow: Excess damage may hit additional targets.

11. Damage Scaling & Step Dice

• Each +1 damage bonus moves you up one Step.
• The “1dX” cycles back from Step 1 as needed.

Quick Reference:

• Step Dice: Determines damage scale.
• +1 Bonus: Increments the damage step.

12. Damage Conversion

Quick Reference:

• Conversion: Map total roll to final damage.
• +4 Increment: Each extra 4 points increases damage by 1.

13. Soak

• Formula: Soak = (AC − 10) ÷ 2, rounded down.
• Apply Soak after damage conversion.
• A natural 20 bypasses Soak.
• A natural 1 causes the attacker to take damage instead (no Soak applied).

Quick Reference:

• Soak Calculation: (AC – 10) ÷ 2.
• Nat 20/1: Special rules apply.

14. Spellcasting

• MP = 5 + your casting stat modifier.
• Spell Save TN = caster’s full stat score (target’s saving throw).

MP Recovery:
At the start of each new day (after an 8‑hour long rest), a character automatically recovers 1d4 MP. This represents the natural replenishment of magical energy through rest and focus.

HP-to-MP Conversion:
During a short rest or as a free action, you may choose to sacrifice a portion of your HP to recover additional MP. Use the conversion:

• For every 2 HP sacrificed, you recover 1 MP.

This optional sacrifice must be used judiciously during encounters when extra MP is needed, balancing the immediate cost of HP loss against the benefit of increased magical capability.

Casting Paths:

• Ash-Binder: +1 MP, always roll 1 Risk Die.
• Veilwalker: 1/day ignore a failed spell.
• Whisperbound: +1 die, take 1 HP.
• Runesmith: Store 1 spell in an item (1/day).

Quick Reference:

• MP & Save: MP = 5 + modifier, TN = casting stat.
• Recovery: 1d4 MP per day; convert 2 HP → 1 MP optionally.
• Casting Paths: Specialize for different magical styles.

Spells (Ideas)

This table lists 50 spells available in One Hero Engine. The Paths column indicates which archetypes or class concepts can adopt the spell (e.g., Arcane for general magic, Necromancer for dark/death magic, Veilwalker for illusions/shadow, Whisperbound for mind/forbidden lore, and a composite group for Cleric/Paladin/Monk/Ranger). MP costs, ranges, and effects are intended as guidelines and may be adjusted to fit your campaign.

MP Boost Ideas

To add depth and strategic flexibility during casting, consider these options for “overcharging” spells:

• Overcharge for Increased Damage:
  Spend 1 extra MP on a damage spell (e.g., Magic Missile) to upgrade its damage one Step higher than normal.

• Extended Duration:
  For buff or defensive spells (like Arcane Shield or Sacred Barrier), spending an extra MP increases the duration by one round.

• Widened Area:
  For spells with an area effect (e.g., Radiant Burst or Nature’s Wrath), an additional MP cost may expand the area of effect or allow the spell to affect an extra target.

• Chain Casting:
  Some spells (such as Spell Echo or Arcane Recall) can be boosted by extra MP to allow immediate recast or restoration of another cast spell during the same turn.

• Enhanced Save Difficulty:
  For spells imposing conditions (like Mind Shatter or Forbidden Words), spending extra MP can force targets to suffer a harsher penalty on their saving throws.

These MP boost options add a layer of resource management and tactical choice, letting players decide when it is worth sacrificing extra MP for an amplified effect.

Use this spells table and MP boosting ideas to create a rich and varied magical repertoire for your One Hero Engine games, tailoring spell choices to your character’s flavor and the challenges of your story.

15. Mythic Spells

• Use once per session.
• Cost: 3+ MP. Always succeeds (no roll).

Examples:

• Chronoseal – Take 2 turns in a row.
• Ashgate – Open a portal.
• Wound the World – Corrupt a location.

Quick Reference:

• Mythic Spells: Rare, powerful spells used once per session.
• Cost & Effect: 3+ MP; automatic success.

Part III: Storytelling Tools

16. Oracle & Twist Points

The Oracle resolves yes/no questions and generates narrative twists.

How It Works:

1. Ask a yes/no question.
2. Roll 2d6:
   • Chance Die represents hope/fortune.
   • Risk Die represents danger/chaos.
3. Add an extra chance or risk die as needed based on Tags or circumstances.

Die Interpretation:

Result Table:

Twist Points:

• You gain 1 Twist Point when dice are equal, a Trait or Spell grants it, or a major failure is narratively impactful.
• At 3 Twist Points, you must introduce a dramatic twist (e.g., an unexpected NPC, reality warps, or a new threat emerges).
• You may also spend a Twist Point before reaching 3 to add a complication, alter a scene, or foreshadow danger.

Quick Reference:

• Oracle: Resolves narrative questions via 2d6.
• Twist Points: Accumulate for dramatic changes at 3 points.

17. Legacy, Scars & Conditions

Scars

Permanent drawbacks incurred from trauma or dramatic failure.

Examples:

• Crippled Arm: Cannot use two-handed weapons.
• Claustrophobic: Disadvantage in tight spaces.
• Broken Faith: Unable to benefit from divine powers.

Legacy

Permanent boons earned from acts of heroism or destiny.

Examples:

• Oracle-Touched: +1 to all Oracle rolls.
• Ash-Bound Soul: Gain +1 MP per session.
• Scar of Glory: Forces enemy Morale checks on sight.

Conditions

Temporary effects that impact your hero’s rolls or overall status.

Examples:

• Poisoned: Disadvantage on CON Saves.
• Stunned: Lose one action.
• Weakened: -1 Step on damage rolls.

Quick Reference:

• Scars: Permanent drawbacks.
• Legacy: Permanent enhancements.
• Conditions: Temporary impairments.

18. Trait Design Guide

Design Traits That Are:

• Flavorful & Balanced: Support Combat, Roleplay, or Hybrid play.
• Timed: Passive, 1/session, or Triggered.
• Evolvable: Adapt as the character levels.
• Narrative-Fitting: Reflect your hero’s background and style.

Types of Trait Effects:

• Bonuses to rolls, stats, or saves.
• Oracle manipulation.
• Spellcasting enhancements.
• Movement, reaction, or status effects.

Upgrade Ideas:

• Add rerolls or extra uses.
• Increase bonus dice or extra steps.
• Introduce situational triggers (e.g., “when wounded”).

Quick Reference:

• Traits: Define unique abilities and bonuses.
• Upgrade: Evolve traits as you level.
• Design: Balance flavor with game mechanics.

19. Example Hero Turns

Kael the Assassin

• Starts in stealth; uses Deathstrike on a cultist.
• Rolls Step 3 (1d8) → converts to 4 damage.
• The cultist dies; Fray damage takes out a second foe.
• Oracle (Risk > Chance) returns “No.” Guards are alerted.

Mira the Paladin

• Activates Aura of Resolve and casts Warding Circle.
• Enemies fail their Morale checks.
• Oracle (Chance > Risk) yields “Yes.” Reinforcements arrive.

Naro the Wizard

• Uses Blood Price to cast a risky spell.
• Sacrifices 1 HP for +2 on his cast.
• Oracle (Equal Dice) yields “Yes, but…” and gains a Twist Point.
• The spell succeeds, igniting nearby vines.

Quick Reference:

• Example Turns: Illustrate tactical and narrative integration.
• Oracle Impact: Decision-making and storyline twists in action.

Part IV: Final Notes

20. Final Words

The story begins with you.

There is no party to carry you.
No game master to guide you.
No one to save you but your own courage and choices.

You are not just playing a game.
You are writing a legend.

You are the last light in the dark. A whisper in the storm.
A name they’ll remember when all others are forgotten.

Pick up your dice. Draw your weapon. Speak your vow.

🎲 One Hero. One Story. Endless Possibilities.

Quick Reference:

• Final Words: Your journey is uniquely yours.
• Inspiration: Embrace the challenge and forge your legend.