Game Master's Guide
The Canula Prime Campaign · Sea · Sky · Faith · Empire · Discovery
Everything a Game Master needs to run Tales of Mar de Oro: session zero, faction pressure, the truth of Éterlumin, source-chamber ruptures, airship conflict behind the screen, the Canula Prime crisis in full, named NPCs, clocks, tables, and campaign paths outward from the Golden Sea.
Contains campaign spoilers. Do not share with players.
GM sections
Everything for running Mar de Oro lives here. Jump into any section. The sticky sub-nav above lets you hop between them without coming back.
GM Guide
Session zero, faction pressure, the truth of Éterlumin, source-chamber ruptures, the Canula Prime crisis, NPCs, tables, and campaign paths.
Jump to chaptersReady-to-run Adventures
The San Telmo Incident (Adventure Zero) includes a PDF quickstart and web edition. Ash on the Ledger (Adventure One), Masks at the Table (Adventure Two), and The Shadowed Tide (Adventure Three) are full web editions. Each supports standalone play where stated.
All four appear in the Adventures hub, in release order.
Browse adventuresShadows of the Compañeros
A complete eight-act Mar de Oro campaign of political intrigue, covert action, aerial warfare, jungle pursuit, and Source discovery.
Includes the GM campaign, spoiler-free player packet, handouts, and four zoomable maps.
Run the campaignGM Tools
Clocks, session objectives, faction moves, clue webs, hard choices, scene spine, consequence planning, end-of-session update. Includes the printable booklet.
Open the toolkitSession Prep Builder
Roll hooks, complications, hard choices, and clue routes; condense scenes to your session length; draft a recap and next-session hooks. Runs in your browser.
Open the builderGM Resources
Every PDF a GM needs, in one place: GM Guide, GM Tools booklet, Shadows of the Compañeros (GM edition, handouts, player packet), plus the player-facing Setting Guide, Character Kit, and One-Page Primer.
Open resourcesSystem-Neutral Adaptation
The six-step ladder for translating this free TTRPG setting into D&D 5e, Pathfinder First Edition, Pathfinder 2e Remastered, Forged in the Dark, or the optional 2d6 Resolution Bridge. Also called system-neutral. Printable Adaptation Worksheet included.
Open the chapterFirst-party rules
Tales of Mar de Oro: Native Rules
The complete first-party game for this setting: Capability, Risk and Effect, Callings, Strengths, Techniques, Fortera, ships, and threats. Nothing here is mandatory — the setting stays system-neutral — but if you want a full rules engine written for Mar de Oro, start here. The optional 2d6 Resolution Bridge remains the ultralight standalone alternative.
Or choose an external rules layer
Run Mar de Oro in the system you already know
The setting is system-neutral. Start with the adaptation framework, then choose a published conversion. Fifth Edition has the most extensive online rules support, while Pathfinder First Edition, Pathfinder 2e Remastered, and Forged in the Dark adapt Mar de Oro through their native rules engines.
Chapters
Session Zero and the Weight of the World
"This setting asks players to stand inside cruelty and decide what they will do about it. Agree on that before the first die falls."
Set tone, lines, and veils before the first scene. Mar de Oro is a beautiful place built on ugly foundations, and it only works if everyone at the table chose to be there.
Open chapterChapter IHow to Run Mar de Oro
"The visible mission is only the door. The real adventure begins when someone asks who built the door, who paid for the key, and what wakes behind it."
The three-layer adventure model, session rhythm, and what success and failure actually look like at the table.
Open chapterChapter IIThe GM's View of the Setting
"The world is older than the empire that named it. The empire is older than it admits."
What the players see versus what the GM knows. The five tensions that drive the campaign, and how to deliver setting without lecturing.
Open chapterChapter IIIFactions in Motion
"Every faction acts whether the characters watch or not."
The major factions with objectives, secret pressures, red lines, and default responses, plus the between-session faction turn.
Open chapterChapter IVSecrets of Éterlumin
"It is not a fuel. It is a response."
Éterlumin as a responsive, volatile gas. States, grades, source chambers, and the faults that make it dangerous at the table.
Open chapterChapter VSource Chambers and Rupturum Events
"A rupture is not an accident. It is an answer."
The rupture scale from minor pulse to campaign-changing catastrophe, and how to run a chamber scene through observation, choice, and cost.
Open chapterChapter VIAirship Conflict Behind the Screen
"The ship is not the setting. The ship is a character with a wound count."
Condition, position, and command. How each power fights, and a damage menu that keeps sky battles moving.
Open chapterChapter VIIBattlefields, Fog of War, and Army Scenes
"Do not run the army. Run the pressure around the characters."
Large battles as living pressure around the characters, not full army simulations. Zones, tracks, fog-of-war levels, and worked battlefield frames.
Open chapterChapter VIIICanula Prime, GM Version
"The island knows more than the administrators who named it."
The island beneath the flags: what everyone knows, what the GM knows, and the sealed basement door with its untranslated warning.
Open chapterChapter IXThe Canula Prime Crisis
"The crisis did not begin with the fire. The fire was the fourth thing."
The full sequence behind the crisis, the missing crewman Emilio Resa, the crisis pressure tracks, and the estate set-piece.
Open chapterChapter XNPCs and Power Players
"Every important NPC has a public face, a private motive, a secret, a fear, and a move they make when cornered."
The named NPCs of the Canula arc, each with the pressures that make them play at the table.
Open chapterChapter XIClocks, Consequences, and Escalation
"A clock is not a threat. It is a promise."
Clock types, how to use consequences without punishing players, and escalation thresholds that change the kind of scene the characters are in.
Open chapterChapter XIITables for Play
"The table is not a crutch. It is a trigger."
Roll tables for harbor activity, NPC encounters, chamber phenomena, and faction moves, for when the players turn left.
Open chapterChapter XIIIThe Éterlumin Economy
"The ledger is the weapon. The convoy is the argument. The source is the throne."
The supply chain from source chamber to contraband stream, the marks on a canister, and prop labels you can hand to players.
Open chapterChapter XIVCampaign Paths After Canula Prime
"The crisis ends. The consequences sail."
Six paths out of the Canula arc, each with a trigger, a central question, and a way to follow the players' strongest choice.
Open chapterAppendixQuick Reference for the GM
"Use this when the table is waiting and the sea has already turned."
Core GM rules, a fast scene builder, and a names-on-the-fly table for when the players ask who this person is.
Open chapterAppendixRunning the Campaign at the Table
"The fastest way to run Mar de Oro is to know who moves next."
A one-page Run Tonight sheet, session prep that survives player freedom, the Canula relationship web, and the law-and-pressure scale from rumor to diplomatic incident.
Open chapterAppendixSystem Guides and Conversion Notes
"Convert the pressure, not every number."
Universal conversion principles, system-neutral procedures, and ready-to-use crunch packs for D&D 5e, Pathfinder First Edition, Pathfinder 2e Remastered, and Forged in the Dark.
Open chapterBehind the screen
Running Mar de Oro at the table
Which rulesets does the GM Guide support?
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The Appendix ships crunch packs for D&D 5e, Pathfinder First Edition, Pathfinder 2e Remastered, and Forged in the Dark, alongside a universal conversion ladder that maps stats, saves, DCs, and consequences across those engines.
How do I convert stats between systems?
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Open the Appendix chapter, pick a system in the sticky selector, and the ladder highlights that engine's column while the crunch pack filters to its native mechanics. You can also download the filtered ladder and crunch pack as a system-specific PDF.
Where is the San Telmo Plantation scenario?
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The San Telmo Incident is a complete adventure available online and as a downloadable Quickstart PDF. The GM Guide also provides supporting material for the plantation, its map, and hazards.
Is the GM Guide safe to share with players?
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No. It contains campaign spoilers, faction pressure clocks, and the truth of Éterlumin as authors of the setting know it. Send players to the Setting Guide or the One-Page Primer instead.
How does the GM Guide handle airship combat and Éterlumin ruptures?
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Airship subsystems, hazard states from Stable to Rupturing, and system-neutral fog-of-war procedures are broken out so you can run naval, aerial, and army-scale scenes without switching frameworks mid-session.
What is Fortera?
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Fortera is the underlying physical field behind the setting's anomalous effects and technologies. Éterlumin is a physical gas/source medium used in systems that interact with that field. It is not Fortera in an excited state.
Does the setting have real physics under it?
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Yes. Mar de Oro is built on a science-fiction spine: Éterlumin and Fortera follow field rules, assay pressures, and tidal models that the GM can predict and exploit. The world feels magical to its inhabitants, but behind the screen the phenomena are consistent enough to run like a puzzle rather than a whim.
Mar de Oro Game Master Area
This is the Game Master side of Tales of Mar de Oro: campaign chapters, session preparation tools, and running guidance for the Golden Sea. It is open to anyone, but it is written for the person behind the screen.
Campaign spoiler warning: the material past this point includes faction secrets, hidden truths, and the sequence of events behind the campaign. Reading it as a player will hollow out surprises the setting depends on.
Spoiler-free GM resources you can open without entering: Mar de Oro GM Tables and new Game Master onboarding.
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