House Rules
System: D&D 5e Modified | Setting: One Piece Universe Campaign: Grand Line Adventures | Balance: Narrative + Tactical
Overview
This campaign uses D&D 5e core rules as the foundation but incorporates significant modifications to fit the One Piece setting. These house rules ensure the game feels authentically pirate-themed while maintaining balanced, fun gameplay.
Philosophy:
- Rule of Cool: If it’s awesome and fits the setting, we’ll make it work
- Narrative First: Story trumps strict RAW when appropriate
- Player Agency: Players encouraged to be creative with abilities
- Balance: No single character should overshadow others
Character Creation
Ability Scores
Method:
- Standard Array: 15, 14, 13, 12, 10, 8
- Point Buy: 27 points (standard 5e rules)
- Rolling: 4d6 drop lowest (if DM approves, all players must use same method)
Racial Bonuses:
- Standard 5e racial ability score increases apply
- Custom lineage allowed (Tasha’s rules)
Races in One Piece
Available Races: The following 5e races represent One Piece world inhabitants:
| 5e Race | One Piece Equivalent | Notes |
|---|---|---|
| Human | Human | Most common, versatile |
| Elf | Skypeian (winged humans) | Wings grant flight, live on Sky Islands |
| Dwarf | Tontatta (small folk) | Rare, fast, strong despite size |
| Halfling | Child-like humans | Regular humans, smaller stature |
| Half-Elf | Mixed heritage | Half-Skypeian, half-Fishman, etc. |
| Dragonborn | Ancient race | Extremely rare, dragon-like humanoids |
| Tiefling | Demon-touched | Rare, often outcasts |
| Tabaxi/Shifter | Mink Tribe | Animal-human hybrids (Luna’s race) |
| Triton | Fishman/Merfolk | Aquatic races, strong swimmers (immune to Devil Fruit water weakness if no fruit) |
| Warforged | Cyborg/Modified Human | Technological augmentation (Llewyn’s cybernetics) |
| Custom Lineage | Any concept | Work with DM |
Classes in One Piece
Standard 5e Classes Allowed:
- All official 5e classes available
- Reflavored to fit pirate theme
Common Reflavors:
| 5e Class | One Piece Flavor | Example |
|---|---|---|
| Fighter | Swordsman, Brawler | Zoro-style sword user, Sanji-style kicker |
| Rogue | Thief, Assassin, Navigator | Nami-style navigator, Luna-style cat burglar |
| Wizard | Scholar, Scientist | Research-focused, gadgeteer |
| Cleric | Priest, Medic | Sylen’s Sun Mother priest, Chopper-style doctor |
| Ranger | Sniper, Hunter | Llewyn’s marksman, Usopp-style sniper |
| Bard | Musician, Performer | Nora’s skald, Brook-style musician |
| Barbarian | Berserker, Wrestler | Raw strength fighter |
| Paladin | Marine, Revolutionary | Sworn oath, justice-focused |
| Warlock | Devil Fruit User (alt) | Patron = fruit’s curse |
| Monk | Martial Artist | Fishman Karate, CP9 Rokushiki |
| Druid | Zoan User (alt) | Animal transformation |
| Sorcerer | Natural Ability | Innate powers (non-fruit) |
Devil Fruits
Integration:
- Devil Fruits function as additional class features (not replacement)
- Charge-based system (see Devil Fruit Mechanics)
- Players can have Devil Fruit OR be strong swimmer (not both)
- Not required (Luna has none, remains viable)
Acquisition:
- Starting characters may begin with Devil Fruit (DM approval)
- Can acquire during campaign through story
- One per character (eating second = death)
Balance:
- Devil Fruit users: powerful abilities, water weakness
- Non-users: can swim, may learn Haki earlier, rely on skill
Combat Modifications
Action Economy
Standard Actions:
- Action, Bonus Action, Reaction, Movement (standard 5e)
- Free object interaction (standard 5e)
Bonus Action Flexibility:
- If class/fruit grants multiple bonus actions, choose one per turn
- Cannot use two different bonus actions in same turn
Critical Hits
Critical Success (Natural 20):
- Attacks: Double damage dice (standard 5e)
- Ability Checks: DM discretion (epic success, additional benefit)
- Saving Throws: Automatic success + potential bonus
Critical Failure (Natural 1):
- Attacks: Automatic miss (standard 5e)
- Ability Checks: Dramatic failure (DM describes consequence)
- Saving Throws: Automatic failure (standard 5e)
Narrative Crits:
- Players encouraged to describe epic crits
- DM may grant additional narrative benefits
Flanking (Optional)
Flanking Advantage:
- Two allies opposite sides of enemy (standard grid rules)
- Both gain advantage on melee attacks
- Encourages tactical positioning
(Alternative: +2 Bonus):
- Instead of advantage, grant +2 to attack rolls
- DM chooses variant before campaign
Death & Dying
Death Saves:
- Standard 5e rules (3 successes = stable, 3 failures = dead)
- Natural 20: Regain 1 HP, stand up
- Natural 1: Counts as 2 failures
Massive Damage:
- Damage exceeding max HP by max HP value = instant death
- Example: 30 max HP, taking 60 damage in one hit = instant death
Resurrection:
- Extremely difficult in One Piece setting
- Rare Devil Fruits may allow (Brook’s Yomi Yomi no Mi)
- Otherwise, death is permanent (high stakes)
Healing
Standard Healing:
- Hit Dice on short rest (standard 5e)
- Full HP on long rest (standard 5e)
- Healing spells/abilities (standard 5e)
Devil Fruit Healing:
- Horu Horu no Mi: At-will healing (2d8+3 per action)
- Other fruits may have healing effects
Medical Treatment:
- Medicine check to stabilize dying character (standard 5e)
- Healer’s Kit grants advantage or automatic success (DM discretion)
Exploration & Travel
Naval Travel
Ship Speed:
- Standard sailing ship: 2 mph (48 miles/day)
- Fast ships: 3-4 mph (72-96 miles/day)
- Calm Belt: Half speed (no wind, must row or special propulsion)
Weather:
- Grand Line has unpredictable, extreme weather
- Navigator checks (Survival, Nature) to avoid storms
- Failed checks: Storm encounter, potential ship damage
Random Encounters:
- Sea Kings (giant monsters)
- Marine patrols
- Pirate crews
- Merchant vessels
- Mysterious islands
Rest & Downtime
Short Rest:
- 1 hour, spend Hit Dice to heal
- Regain some class features (per class rules)
- Devil Fruits: No charge regeneration
Long Rest:
- 8 hours (6 sleep, 2 light activity)
- Regain all HP and Hit Dice (up to half total)
- Regain all class features and spell slots
- Devil Fruits: Regain ALL charges
Interrupted Rest:
- Combat longer than 1 minute interrupts rest
- Must restart rest from beginning
Downtime Activities
Crafting:
- Standard 5e rules
- Gadgeteers (Gluthoric) can craft special items
Training:
- Learn new skills, languages, tool proficiencies
- 250 days of downtime (standard 5e)
Carousing:
- Make contacts, gather rumors
- Roll on carousing table for results
Social & Roleplay
Bounties
Wanted Posters:
- Pirates and criminals receive bounties (Berry currency)
- Higher bounty = more dangerous/notorious
- Marines and bounty hunters pursue high bounties
Current Party Bounties:
- Flynn: 2,500,000 berries (only PC with active bounty)
- Others: None (yet)
Increasing Bounty:
- Major crimes: attacking Marines, destroying towns
- Defeating famous pirates
- Acquiring dangerous Devil Fruits
- DM assigns bounty increases based on notoriety
Reputation
Fame & Infamy:
- Actions affect how NPCs react to party
- Pirates may respect high bounties
- Civilians may fear or revere crew
- Marines track and pursue notorious pirates
Tracking:
- DM tracks party reputation with major factions
- Reputation affects quest availability, prices, NPC attitudes
Companions & Pets
Companion Scaling
Marksman’s Beast of the Land (Howitzer):
- HP: 6 + (Marksman level × 6)
- AC: 13 + Proficiency Bonus
- Attack Bonus: STR mod + Proficiency Bonus
- Damage: Weapon damage + STR mod + Proficiency Bonus
- Saves/Checks: Add Proficiency Bonus (Primal Bond)
Gadgeteer’s Iron Defender (Inductor):
- HP: 5 + (Gadgeteer level × 5) + CON mod
- AC: 14 natural + 3 deflection = 17
- Attack Bonus: STR mod + Proficiency Bonus
- Damage: 1d8 + STR mod + Proficiency Bonus (force damage)
- Saves: Equal to Gluthoric’s (if higher)
Other Companions:
- Use standard 5e stat blocks
- Scale with character level (DM discretion)
Currency & Economy
Berry System
Conversion (Rough Guide):
- 1 gold piece (GP) = 10,000 berries
- 1 silver piece (SP) = 1,000 berries
- 1 copper piece (CP) = 100 berries
Prices:
- Common gear: Standard 5e prices converted
- Devil Fruits: 100,000,000+ berries (if purchasable)
- Ships: 10,000,000 to 1,000,000,000 berries
Treasure
Pirate Hoards:
- Gold, jewels, art (standard D&D treasure)
- Devil Fruits (rare)
- Maps to legendary locations
- Rare materials (seastone, Adam Wood)
Bounty Rewards:
- Turning in wanted pirates pays bounty amount
- Marines pay full bounty
- Some factions pay partial bounty
Magic & Technology
Magic in One Piece
Limited Magic:
- No traditional wizards casting fireballs (unless Devil Fruit)
- “Magic” comes from Devil Fruits, Haki, or rare artifacts
- Clerics/Paladins reflavored as faith-powered (Sun Mother grants Sylen’s powers)
Spell Reflavoring:
- Fireball = Bomb Ball (Bomu Bomu no Mi)
- Cure Wounds = Hormone Healing (Horu Horu no Mi)
- Misty Step = Spring Hopper (Bane Bane no Mi)
Technology Level
Advanced Technology:
- Cyborgs and robotics exist (Llewyn, Inductor)
- Firearms common (flintlock pistols, rifles, cannons)
- Gadgets and inventions (Gluthoric’s gadgeteer items)
- No computers or modern electronics
Dial Technology:
- Sky Island exclusive (store wind, fire, impact, etc.)
- Rare in Blue Sea
- Can be incorporated into gear
Haki
Haki System:
- Spiritual power available to anyone (not just Devil Fruit users)
- Three types: Observation, Armament, Conqueror’s
- Unlocked through training (usually mid-to-high levels)
- See Haki System for full mechanics
Current Party Haki:
- None yet (low level)
- May unlock at level 5+
Alignment & Morality
Flexible Alignment
Alignment as Guide:
- Alignment describes character, doesn’t restrict actions
- Character can act outside alignment occasionally
- Repeated actions may shift alignment
Pirate Morality:
- Not all pirates are evil (some are freedom-seekers)
- Marines aren’t always good (corrupt officers exist)
- Gray morality encouraged
Miscellaneous Rules
Inspiration
Earning Inspiration:
- Great roleplay moment
- Clever solution to problem
- Heroic sacrifice or dramatic choice
- Making table laugh or creating memorable moment
Using Inspiration:
- Spend to gain advantage on any d20 roll
- Can only have 1 inspiration at a time
- Can’t stockpile
Surprise
Surprise Rounds:
- Stealth check vs. Passive Perception
- Surprised creatures can’t move or take actions on first round
- Lose reaction until end of turn
Falling
Fall Damage:
- 1d6 per 10 feet fallen (standard 5e)
- Maximum 20d6 (200 feet)
Devil Fruit Negation:
- Bane Bane no Mi: No fall damage (spring absorption)
- Other fruits may mitigate (flight, cushioning)
Underwater Combat
Standard 5e Rules:
- Creatures without swim speed have disadvantage on attacks
- Melee attacks only (ranged weapons don’t work)
- Difficult terrain (movement costs double)
Devil Fruit Users:
- Cannot fight underwater (incapacitated when submerged)
- Must be rescued by allies
Optional Rules (DM Choice)
Gritty Realism (Probably Not Used)
- Short rest = 8 hours
- Long rest = 7 days
- Makes resources more precious (likely too harsh for pirate adventure)
Feats (Recommended)
- Allow feats at ASI levels (standard 5e optional rule)
- Increases build variety
- Encourage creative character concepts
Multiclassing (Allowed)
- Standard 5e multiclass rules
- Must meet ability score prerequisites
- Encourages hybrid builds (Pirate/Marine, Sniper/Brawler, etc.)
DM Rulings
Rule Zero
DM Has Final Say:
- When rules unclear, DM makes ruling
- Rulings made quickly to maintain pace
- Can be discussed after session
Consistency:
- Once ruling made, DM keeps it consistent
- Rulings added to house rules if recurring
Rule of Cool
Favor Awesome:
- If player suggests something cool and narratively fitting, DM tries to allow it
- May require check or resource expenditure
- Encourages creative play
Related Pages
rules house-rules system mechanics campaign
Last Updated: 2025-11-03