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Game Master Guide

The Game Master describes things in the world, and narrates what happens in response to player actions. Here are some tips and tricks for running the game.

You can find a one-page GM cheatsheet on the downloads page.

The Guiding Principles

There are three core principles to running a game of Adventure.

  1. Rulings, not rules. The narrative is more important than rules and mechanics. If the rules get in the way or don’t quite fit, ignore them.
  2. Portray a fantastic world. The worlds you explore should be full of awe, wonder, mystery, danger, and humanity.
  3. Play to find out what happens. Your stories don’t have predetermined endings. Give players meaningful choices that drive the narrative.

Starting the Game

Start a game of Adventure by describing the fantastic location or tense situation the players find themselves in. Throw them right into the action.

Then, ask them questions about why they’re there, what they know, and how they know it. Use their answers to give the world depth and drive the game forward.

Finally, end with a call-to-action: “What do you do?”

Example: The Isle of the Kraken

A Fantastic Location

Once every few years, a tiny island mysteriously rises from the depths of the sea for just a few hours. It never appears in the same place twice. Sometimes, it disappears before anyone’s even taken notice.

In the center of the island is a stone monolith, a small tower with a carving of a kraken at the top. It’s rumored that a powerful wizard who lived there thousands of years ago hid a legendary artifact somewhere on the island.

Many an explorer has ventured to the island searching for it. None have returned. Tonight, the island has surfaced again. You’re in a rowboat, headed in the direction it was allegedly seen. Water laps at the low sides of the boat. Suddenly, you catch sight of it.

In the distance, you see the monolith, the carving of the kraken lit brightly by the full moon above. How long has the island been at the surface? How much longer until it disappears again?

You row harder…


  • How did you learn that the island had resurfaced?
  • What artifact is hidden there? What is it rumored to do?
  • Why are you interested in exploring the island or retrieving the artifact?
  • What do you know of the wizard who used to live there?
  • Who else might be interested in the island or artifact?


As you approach the shore, you see a ship moored to a tree, a black flag with two crossed tridents flapping in the gentle breeze. You notice two pirates asleep next to the tree. Foot prints lead into the forest towards the monolith.

What do you do?

Creating a Fantastic World

As a GM, you want create a fantastic world for the players to explore.

Identifying a few aspects of your world ahead of time can make it a lot easier to improvise, respond to what your players do, and breathe life into your world.

  • Fantastic Locations. Amazing places that the players can explorer, with a few details and unique features. Imagine a place that’s really big, really old, or really weird.
  • Dangers. What kind of creatures live there? What sort of natural obstacles might they encounter? What traps might have been set to keep trespassers away?
  • Secrets. As players explore the world, they’ll uncover secrets and hidden mysteries. Identify a few that you can reveal when it makes sense in the story.
  • Treasure & Magic Items. Treasure and magic items can reveal secrets about the world, drive a quest, or give the players new powers and abilities.
  • Fronts. The big players and forces in a campaign, these are things that will affect the world and unfold in sequence unless the players intervene. One to three are good for a short campaign, but you can have five or more for a bigger one.

These are modular, and designed be dropped into the story whenever appropriate.

Example: Isle of the Kraken


  • A mysterious island that emerges from the sea every few years. A ship moored to a tree, with a black flag featuring two crossed tridents. A tall monolith protruding from the trees. Sleeping pirates and empty rum.
  • Jellyfish Lake. A massive cavern with huge subterranean lake. Jellyfish fill the water, glowing blue/purple. A rowboat with no oars waits on the shore.
  • Tentacle Gate. Big iron gate, slats woven tentacles. Kraken head at the top, with a gem in one eye, missing in the other. A pile of rocks nearby.


  • Crabs
  • Giant Crabs
  • Pirates
  • Pirate captain
  • Lightning Eels
  • Magic Manta Ray
  • Glow Jellyfish
  • Kraken

Treasure & Magic Items

  • Seaweed of Speed. When consumed, the person who eats this seaweed is able to run twice as fast as they normally could.
  • Armor of the Leatherback Turtle. Automatically heals one moderate injury at the end of any combat encounter.
  • Whale Ward. A wooden necklace carved into the shape of a whale, prevents one fatal injury. Loses all magical properties after being used.
  • Staff of the Merfolk Shaman. A staff of fiery red coral, grants its possessor advantage to spell rolls, and access to the following spells: Shell Skin, Wall of Waves, and Coral Growth.
  • Merrow Trident. Seems to magically find its mark. User gets advantage on all attack rolls.


  • A kraken guards the islands treasures, and hunts intruders
  • A group of fishfolk cultists worship the kraken and live there
  • One of the pirates is not there of his own will
  • The Pirate Captain wants to use the artifact to destroy one of the characters’ home town
  • The artifact was stolen from Pirate Captain’s family (or so he was told)
  • The Island is actually a giant, ancient turtle


  • Fishfolk Cultists. Want to harness the powers of the island and expand beyond the fringes.
    1. Collect and steal magic items, gold, and prisoners
    2. Reproduce old wizard’s experiments
    3. Gain control of the kraken and/or island
  • Pirates. Reclaim the artifact for their people and exact revenge.
    1. Locate the artifact
    2. Figure out how to unlock its power
    3. Attack the mainland
  • Turtle Island. Return to the depths after getting some air.
    1. Deep bellowing, rushing air, gurgling
    2. Several rumbles or tremors
    3. Total collapse, massive earthquake

Story & Mechanics

Your primary role as a GM is translating story elements into mechanics and back again. Here are some tools to help you do that more easily.

Accounting for Difficulty

Under the die roll system, every action has the same probability of succeeding (or not). But some actions are inherently more difficult than others.

In addition to advantage and disadvantage mechanics, you can account for difficulty in complex situations by breaking each step into its own die roll.


A player is trying to run up to a giant, scale his 20-foot high boot, and hit him with a sword. This would involve three separate die rolls.

  1. A roll to sneak up to the giant undetected (or avoid obstacles thrown at you while approaching).
  2. Another roll to scale the boot without falling or getting knocked off.
  3. A third roll to see if the hit with the sword does anything.

Fail Forward

Statistically, failed die rolls will happen about a quarter of the time a player rolls.

Failure should still drive the narrative forward. It’s far more interesting than simply saying, “No, that didn’t work.”


  • The player fails to pick the lock on the chest. It springs a trap, causing the room to lock and start filling with water!
  • The player tries to jump across a cliff and fails the roll. They slam into the cliff wall and fall onto a ledge 20 feet down. They think they’ve escaped the worst of it… until the ledge starts to shift and crack under their weight.

Common Actions & Outcomes

There are a handful of types of player actions that happen frequently in adventure. Here are some ideas for improvising outcomes for them.

Cast Spells
When casting a difficult or powerful spell…
  • 9+ The spell works
  • 6-8 It also draws unwelcome attention or goes out-of-control
When making an attack…
  • 9+ Your attack lands
  • 6-8 The enemy also hits you or you get put in a tough spot
Defy Danger
Any time you try to avoid danger or getting hurt…
  • 9+ You succeed
  • 6-8 You stumble, and choose from a worse outcome or tough choice
When you try to defend yourself of a teammate from an attack…
  • 9+ Block the attack
  • 6-8 Lessen the damage, or block all of it but damage your armor or weapon
Understand the World
Whenever you try to study the world around you, a person, or a situation… On a 9+, the GM answers three questions. On a 6-8, they answer one.
  • What happened here recently?
  • What is about to happen?
  • What should I be on the lookout for?
  • What here is useful or valuable to me?
  • Who’s really in control here?
  • What here is not what it appears to be?
Recall Knowledge
Whenever your character tries to recall something that they would know in the story…
  • 9+ The GM will tell you something interesting and useful
  • 6-8 The GM will tell you something interesting only
When you try to persuade or intimidate someone…
  • 9+ They do what you want
  • 6-8 They do what you want, but require something from you first
Last Breath
When a character is dying…
  • 9+ Death allows them to return to the living
  • 6-8 Death requires something in return

Creating Creatures

Creatures in your world are likely to be quite varied.

  • They may be friendly allies to the party, enemies, or weird and wondrous creatures.
  • Their health rules probably differ from player characters (they might be weaker, stronger, or virtual invincible).
  • Focus on the narrative, and what makes sense in the world you’re building.
  • Most creatures will flee a fight if they think they’re going to lose.


  • A friendly gnome, lost in the tunnels for a week, is offered food by the party. To show her gratitude, she leads them to a glowing sword she discovered, wedged firmly into a rock.
  • A swarm of rats rushes at the wizard. He launches a fireball at them, instantly vaporizing a dozen of them.
  • The archer shoots arrow after arrow at the dragon. Each one bounces off its tough scales. The creature doesn’t even seem to notice.
  • The pirate captain drops unconscious after being hit with a warhammer. Sensing the shift in the battle, three of his crew take off running down the tunnel. The remaining pirates lay down their swords in surrender.

Treasure & Magic Items

One of the most exciting parts of exploring fantastic locations is finding treasure and magic items that grant characters new abilities.

The most meaningful items are tied to the locations where they’re found, and provide some kind of minor benefit or magical effect. What’s the story behind them? How do they thematically tie into your world?


The Isle of the Kraken was home to merfolk wizard who spent his days experimenting on sea creatures and crafting items from their magical properties.

Armor of the Leatherback Turtle
Automatically heals one moderate injury at the end of any combat encounter.
Seaweed of Speed
When consumed, the person who eats this seaweed is able to run twice as fast as they normally could for about an hour.
Ring of Aquatic Beasts
A ring made of abalone. The wearer rubs ring and names an aquatic animal. On a successful roll, they acquire 1-2 traits from that animal.

Traps & Obstacles

Signal serious dangers to players. Don’t surprise them with danger they can’t avoid. Put traps in plain sight.

The more dangerous it is, the more obvious it should be.

Give players opportunities to solve problems and interact with the world. Reward creativity and problem-solving.

How to Build Traps

Duration and Complexity

Games of Adventure can take as little as 30 minutes or last several hours.

As the Game Master, you have a lot of control over the length and complexity of each game. You can add or remove creatures, reveal or discard secrets, adjust the HP of creatures, and save the day with NPCs.

You can also spread an adventure over several sessions, stopping after an encounter, and picking things back up another time.

Additional Resources