Starfinder 2E GM Core - Chapter 2: Building Games

Source: https://2e.aonsrd.com/rules/740-chapter-2-building-games

Last Updated: 2026-01-14

Overview

"Game Mastering can be an extremely creative endeavor, and this chapter gives you a suite of tools to create your own campaign or adventure." The chapter is organized into sections covering campaign structure, adventure design, encounter design, variant rules, afflictions, environment, hazards, and world-building.

To Create or Adapt

Before building custom content, consider three questions:

1. Does something similar already exist?
2. What needs changing between your idea and existing material?
3. How much preparation time do you have?

Scope of Changes

GMs can use default rules and published settings, or create entirely new content. "The most important thing remains creating a story collaboratively with the rest of your group while having fun."

Campaign Structure

Campaign Length

Campaigns range from a few sessions to many years. General progression estimates:

• Playing weekly for a year: ~14-level campaign
• Playing biweekly for a year: ~8-level campaign
• Playing monthly for a year: ~5-level campaign

Some campaigns reach 20th level; others end at lower levels after defeating major villains. "You should have an end point in mind when you start a campaign. Still, you have to be flexible."

Basic Structures

One-Shot

• Adventures: 1
• Top Level: 1 (often higher)
• Time Frame: 1 session

Brief Campaign

• Adventures: 2
• Top Level: 4-5
• Time Frame: 3 months weekly or 6 months biweekly

Extended Campaign

• Adventures: 5
• Top Level: 11-13
• Time Frame: 1 year weekly or 1.5 years biweekly

Epic Campaign

• Adventures: 6 long adventures
• Top Level: 20
• Time Frame: 1.5 years weekly or 3 years biweekly

Themes

Campaign themes include major dramatic questions, recurring environments, creatures, and genres such as dystopian, high-tech, fantasy, wartorn, horror, and weird. Themes should relate to backstories, motivations, and flaws of player characters and villains.

Linking Adventures

Smooth transitions between adventures include:

• NPCs appearing in multiple adventures
• Treasure or clues from one adventure becoming important in later ones
• Fallout from previous PC choices affecting subsequent adventures
• Related locations in space

Player Goals

GMs should ask what players enjoy and what they want to see. "Find out what each character wants to achieve and look for opportunities you can place in the game world and its adventures." Progress character goals through roleplay and downtime. Reward players who track goals with extra Hero Points.

Changing the World

"As the group moves through the campaign, the events of their adventures and downtime should change the world and galaxy around them." Show changes through NPC reactions, scenery, and environment.

Power Level

As the game progresses, both PCs and foes become more powerful. "Higher-level adventures should present new challenges appropriate to the PCs' abilities." PCs should elicit different reactions as their reputation spreads.

Recurring Villains

Include villains appearing multiple times across adventures. "When you create a recurring villain, it's best not to make them too integral to the story since the PCs might take them down earlier than you expect!"

Villain Goals

Villains should have goals guiding their actions. "Just like with the PCs' goals, show how the villain's goal has impacted the world, even in small ways."

Starting the Campaign

Before the first session, communicate:

• Expected schedule and campaign length estimate
• When/where first session occurs and what to prepare
• Character-building restrictions or extra options
• Game universe location
• Basic genre or theme

At the First Session

• Recap campaign basics
• Have players introduce characters
• Ask questions about characters and note significant details
• Begin adventure using Starting a Session steps

Starting at a Higher Level

PCs all start at the same level. Use the Character Wealth table to determine starting currency and items. "Let the players choose their own items as well as spend their currency on common items if they choose."

Ending the Campaign

Check in with the group about how long they want continuation and if they're having fun. "Ideally, you know at least a session in advance that the end is coming, allowing you to prepare for a thrilling conclusion."

An epilogue makes endings more fulfilling. Let roleplay finish, describe broad results, ask what characters do next, and narrate short scenes.

Dealing with Failure

If a campaign ends prematurely, ask players if they want to continue. Look for ways the campaign might continue even after setbacks.

The Next Campaign

If the next campaign follows in the same setting, "think through the repercussions of the last campaign and change the galaxy as needed." Introduce elements calling back to the previous campaign.

Adventure Design

"Creating an adventure for your players can be one of the most fulfilling parts of being a GM." Adventures can start from antagonists, locations, or other points.

Player Motivations

"One of your most important and rewarding tasks is getting to know your players and what makes them tick." Implement hooks speaking to different player preferences. Different players enjoy epic stories, tactical combat, NPCs, cute creatures, etc. "Knowing their motivations gives you a way to put in elements you expect will appeal to your players, but their decisions will still take the adventure in unexpected directions."

Theme and Feeling

"Think about the emotional and thematic touchstones you want to hit during play." Consider what emotions players should feel: triumph, dread, sadness, optimism, etc.

Keeping it Varied

Provide variety through:

• Types of challenges (combat, social, problem-solving)
• Locations
• NPCs met
• Monsters faced
• Treasure acquired

"Think in terms of sessions. If your group gets through five scenes per session, how do you make one game session feel different from another?"

Adventure Recipes

Eight-step procedures for building adventure skeletons:

1. Styles
2. Threats
3. Motivations
4. Story Arcs
5. NPCs and Organizations
6. Locations
7. Encounters
8. Treasure

Styles

Exploration (3-4 sessions)

• Exploration Scenes: 1 long voyage, 3 trapped hallways/mazes, 1 hangar, 2 secret rooms
• Combat Encounters: 2 trivial, 8 low, 6 moderate, 2 severe
• Roleplaying Encounters: 4 conversations, 1 negotiation
• Tropes: Lasers, cameras, robots, chambers, hallways, traps, puzzles

Dystopian Adventure (5-7 sessions)

• Exploration Scenes: 1 long voyage in space, 2-3 urban/space explorations, 1 heist
• Combat Encounters: 4 trivial, 7 low, 7 moderate, 4 severe, possibly 1 extreme
• Roleplaying Encounters: 2 battles of wits, 2 deception chances, 2 info gathering
• Tropes: Personal stakes, betrayal, ambushes, duplicity, urban disasters, piracy

Horror (1-2 sessions)

• Exploration Scenes: 1 short voyage, 2-4 creepy areas
• Combat Encounters: 2 moderate, 1 severe, possibly 1 extreme
• Roleplaying Encounters: 2 with doubtful authorities, 1 info gathering, 1 horrible truth
• Tropes: Jarring encounters, overwhelming feelings, retreat options

Infiltration (2-3 sessions)

• Exploration Scenes: 1 voyage/tour, 2-3 trapped rooms
• Combat Encounters: 4 low, 4 moderate, 1 severe
• Roleplaying Encounters: 1-2 with security patrols
• Tropes: Secured complexes, goal-oriented victories

Intrigue (2-3 sessions)

• Exploration Scenes: 3-4 competitions, 1-2 infiltrations
• Combat Encounters: 2 trivial, 2 low, 4 moderate, 1 severe
• Roleplaying Encounters: 2-3 battles of wits, 2 political scenes, 1 cryptic source
• Tropes: Urban environments, ambushes, assassination attempts

Military Adventure (2-3 sessions)

• Exploration Scenes: 1 long voyage, 2-3 patrols, 2-3 trapped outposts
• Combat Encounters: 4 low, 4 moderate, 1 severe
• Roleplaying Encounters: 1-2 skill challenges, 1-2 with officers
• Tropes: Fortified battlegrounds, starship battles, goal-oriented victories

Mystery (2-3 sessions)

• Exploration Scenes: 2-3 trapped rooms, 2 puzzles/investigations
• Combat Encounters: 2 trivial, 4 low, 6 moderate, 6 severe
• Roleplaying Encounters: 1 battle of wits, 1 unusual ally, 1 info gathering, 1 reveal
• Tropes: Natural encounter discovery during investigation

Planar Adventure (6-8 sessions)

• Exploration Scenes: 3-4 long voyages through planes, 1-2 scouting scenes
• Combat Encounters: 4 low, 12 moderate, 6 severe, 2 extreme
• Roleplaying Encounters: 4 with bizarre creatures, 4 info gathering
• Tropes: Otherworldly environments, creative battlegrounds

Romantic Adventure (4-6 sessions)

• Exploration Scenes: 1 tour, 1 outskirts adventure, 1 tournament
• Combat Encounters: 2 trivial, 3 low, 6 moderate, 1 severe
• Roleplaying Encounters: 2 battles of wits, 1 gala, 1 entreaty, 2 relaxation scenes
• Tropes: Duels, connections between PCs and foes, rivals becoming lovers

Space Opera (6-8 sessions)

• Exploration Scenes: 2 long voyages, 1 dangerous complex/race
• Combat Encounters: 4 trivial, 10 low, 12 moderate, 4 severe
• Roleplaying Encounters: 2 battles of wits, 4 potential ally conversations
• Tropes: Unique environments, starship boarding, dogfights, large enemy groups

Threats

Corruption Opposition weakens or changes motivation of places, people, institutions, or groups.

• Show corruption effects on people and places
• Make enemies subtle and patient
• Contrast corruption with education and progress
• Expose corruption agents when PCs make progress

Foes: fiends, Midwives, psychic fungus, undead

Devastation Opposition destroys or lays waste to places, people, institutions, ideals, or groups.

• Show destruction effects
• Make enemies hard to reason with
• Contrast devastation with preservation
• Show slow recovery from devastation

Foes: dragons, daemons, Swarm

Extremism Opposition seeks massive change through violent means.

• Demonstrate ruthlessness
• Have enemies focus on their goal
• Show sympathetic sides if applicable
• Show demoralization when PCs make progress

Foes: angels, cultists, jinsuls, terrorists

Mayhem Senseless violence disrupts settlements and natural order.

• Single powerful foe or groups cause mayhem
• Emphasize cascading disruption effects
• Show resilience and recovery

Foes: akatas, beasts, bloodbrothers, dinosaurs, gremlins, orocorans

Subjugation Opposition wants to rule over groups, locations, or the world.

• Show submission to avoid consequences
• Make enemies self-righteous and focused
• Show opposition and rebellion
• Have previously cowed parties rebel

Foes: aeon guards, Corpse Fleet, devils, dragons, imperial troopers, Swarm

Motivations

Consider opposition motivations:

• What do they want?
• Who/what do they fear?
• Why are they sure to succeed?
• What are their weaknesses?

Story Arcs

Keep multiple story arcs in mind with beginning, middle, and end points. "Revisit the end point you've imagined. If the adversary's plan has been derailed, what might they do instead?"

Use touchstones:

• Use motifs and repeated thematic elements
• Follow character growth
• Escalate threats
• Bring in recurring characters
• Make each adventure count
• Make choices matter

NPCs and Organizations

Allied, neutral, and adversarial NPCs and organizations contribute to theme. Include counterpoints to theme for variety. "Including NPCs who aren't adversaries makes the game universe feel more real."

Locations

"Memorable settings that include mysterious and fantastical locations for players to visit can elicit the players' curiosity." Describe details like decorations, landmarks, wildlife, smells, and temperature. Include environment-based challenges appropriate to location.

Encounters

"A robust set of encounters forms the backbone of your adventure." Build appropriate encounters for group level.

Treasure

"Your adventure should give out an amount of treasure that's appropriate to the characters' level." Spread treasure throughout adventures rather than stockpiling in single hoards.

Encounter Design

"Encounters play a fundamental part in roleplaying games, but it can be tricky to know where to start when building them." Good encounters have place in story, compelling adversaries, interesting locations, and dynamic twists.

Combat Threats

Five threat categories exist:

Trivial-threat encounters are essentially unloseable. Characters unlikely to spend significant resources. "A trivial-threat encounter can still be fun to play, so don't ignore them just because of the lack of challenge."

Low-threat encounters present difficulty and typically use party resources. Party unlikely to be seriously endangered.

Moderate-threat encounters seriously challenge characters. "Characters usually need to use sound tactics and manage their resources wisely."

Severe-threat encounters are hardest most groups defeat. "Use severe encounters carefully—there's a good chance a character could die."

Extreme-threat encounters are likely even matches. "Use an extreme encounter only if you're willing to take the chance the entire party will die."

XP Budget

Base XP budget by threat (4-character group):

Quick Adventure Groups

Basic encounter structures (120 XP moderate):

• Boss and Lackeys: 1 party level +2, four party level -4
• Boss and Lieutenant: 1 party level +2, 1 party level
• Elite Enemies: 3 party level creatures
• Lieutenant and Lackeys: 1 party level, four party level -4 (80 XP)
• Pair: 2 party level (80 XP)
• Troop: 1 party level, 2 party level -2 (80 XP)
• Squad: 6 party level -4 (60 XP)

Choosing Creatures

Creatures typically range from party level -4 to party level +4.

Creature XP and Role Table:

Different Party Sizes

For each additional character beyond four, increase XP budget by Character Adjustment amount. For fewer than four characters, subtract correspondingly. "It's best to use the XP increase from more characters to add more enemies or hazards."

Variety

Include varied:

• Themes and creatures
• Difficulty levels
• Complexity
• Encounter composition
• Setup and enemy reactions
• Terrain features

Encounter Locations

"Choose compelling settings for your encounters." Environmental features should reflect occupants' tastes, biology, or wealth. Encounters should match creature motivations and locations.

Maps and Terrain

Consider maneuverability, line of sight, and attack ranges. "Even empty rooms and corridors can provide variety based on their size and shape." Large areas need cover and interesting features. Small spaces favor melee combatants.

Inhabitant or Intruder

Most often, PCs enter territory more familiar to foes. Inhabitants know locations, avoid dangers, or are unaffected by them. Consider creature abilities like burrowing, climbing, or swimming. Sometimes PCs defend their own base, giving them advantage.

Wild Weather

Weather creates challenges: rain slows movement, cold introduces ice, extreme temperatures can impact encounters. "Light levels play a key role in both outdoor and indoor encounters."

Unexpected Infrastructure

Hidden mechanical, electronic, and plumbing features exist in buildings/starships. "You should always feel comfortable explaining to a PC before they waste actions that their character doesn't think the idea is possible given the limited amount of time and resources available during an encounter."

Complex infrastructure actions should take an entire round or more.

Budgeting for Terrain

Tricky terrain or hazardous features might increase encounter difficulty. "Think about the impact of the terrain in advance, especially if the battle would already be a severe threat, or you might kill the party." Consider assigning extra XP if base threat is low/moderate.

Enemy Motivations

"Every encounter should happen for a reason. Consider a creature's motivation to fight." Creatures might defend homes, rob for enrichment, follow impulses, or fight for pay. Unmotivated combat might not need to happen.

Morale

"Think how an enemy reacts when a fight is going poorly for them—or well!" Most creatures—even animals—back down from obviously losing battles. This normally means fleeing but could involve capture or negotiation. "An enemy's morale could even change the encounter from combat to social."

Dynamic Encounters

Use dynamic elements to create more interactive, interesting encounters. These work best for boss fights and memorable encounters. "The more complex a dynamic encounter is, the longer it takes to run and the more demanding it is."

Pitfalls to Avoid

• Don't make every encounter complex
• Avoid flat difficulty
• Beware unexpected difficulty spikes
• Watch for overpowered terrain

Hazards in Combat

Simple hazards combined with creatures can prove perilous. Complex hazards continue to act, offering ongoing encounter presence. "Hazards in combat shine when they give the PCs ways to contribute meaningfully other than dealing damage to a creature."

Evolving Battlefields

Create evolving battlefields with dynamic environmental features, third parties, or state changes. "Major physical changes to the environment, such as the collapsed portions of a room rising and falling or water beginning to rush in and fill the room, can force the PCs to rethink their plans."

Combining and Separating Encounters

Foes taking reasonable countermeasures feels more realistic. "When the PCs' foes amass into an overwhelming force, give the PCs fair warning and a chance to retreat and try again another day."

Separate encounters for dramatic changes like collapsing ceilings or magical barriers.

Time Pressure

"Time pressure adds an extra sense of urgency to any encounter and can be a great way to make an otherwise trivial- or low-threat encounter tactically engaging."

Secondary Objectives

"One of the simplest and most exciting ways to create a dynamic encounter, even if the combat itself isn't so difficult, is to add a secondary objective beyond simply defeating foes." Examples include preventing executions, protecting evidence, preventing retreats, or using nonlethal tactics. These highlight different PC abilities.

Opponent Synergy

Collaborating foes develop additional strategies. Give team members reactions triggered by allies' abilities. Poor coordination between mindless creatures benefits PCs. Synergistic components can represent hive minds or massive creatures.

Misdirection

Use holograms, disguised doubles, illusions, or possession for misdirection. Villains might escape and return with counterstrategies. "Even if the villain doesn't escape, they might have other tricks up their sleeves, such as rising again to oppose the PCs."

Social Encounters

Details on running social encounters appear in the Running the Game chapter. Setup is less detailed than combat. Need NPC statistics for social skills, Perception, and Will using non-combat level.

Social Encounter Examples include:

• Broadcasting deceptions
• Brokering peace
• Convincing NPCs of various actions
• Ending standoffs
• Winning competitions
• Proving innocence
• Securing contracts
• Defeating arguments

Treasure by Encounter

Standard rules count treasure over level. For single-encounter treasure, use threat level:

Treasure by Encounter:

Additional Sections

The chapter also covers:

• Variant Rules: Rule changes offering different play experiences from baseline
• Afflictions: Curses and diseases for use in games
• Environment: Rules for overcoming obstacles and natural hazards
• Hazards: Traps protecting buildings or dungeons
• Building Hazards: Advice for creating custom hazards
• Building Creatures: Top-down approach for constructing creatures and NPCs
• Building Items: Creation of new treasure pieces
• Building Worlds: Building entire worlds or settings from scratch

This document contains the complete mechanical details from SF2E GM Core Chapter 2: Building Games, including all tables, XP budgets, encounter design guidelines, adventure recipes, and treasure values.