# Establish the Rules

> Define what is possible, impossible, costly, and consequential so your world develops believable cause and effect.

- Canonical page: [https://www.summonworlds.com/learn-worldbuilding/establish-the-rules/](https://www.summonworlds.com/learn-worldbuilding/establish-the-rules/)
- Publisher: Summon Worlds by OpenForge LLC
- Last updated: 2026-07-20

Worlds feel believable when actions have understandable consequences. Realism can help, but consistency is what allows an audience to form expectations, notice exceptions, and care when someone takes a risk.

By the end of this step, you will know what is possible, what it costs, and who benefits.

## Define only the rules that matter

Begin with the distinctive truth in your premise. Ask five questions:

1. What makes it possible?
2. What can it never do?
3. What does using it cost?
4. Who controls or understands it?
5. How has ordinary life adapted to it?

You do not need to simulate the entire universe. Define the rules that create choices, shape daily life, or support the experience promised by your pillars.

In Emberwake, living islands can cross the sea, but they cannot be steered directly. Navigators influence them through cultivated coral songs. Each song permanently changes the singer's hearing. That one cost affects status, language, work, disability, and political power.

## Follow consequences outward

For every major rule, trace consequences at three distances:

- **Personal:** What does this change for one person's body, work, or relationships?
- **Social:** What customs, institutions, or inequalities grow around it?
- **World-scale:** What does it change about travel, war, trade, ecology, or history?

This turns a clever mechanism into a source of connected worldbuilding.

## Leave room for mystery

Consistency does not require complete explanation. You may know a rule's effect without knowing its origin. Mystery works when the audience can distinguish the unknown from the arbitrary.

Write down which truths are widely known, which are disputed, and which are secrets even you may discover later.

## Create it in Summon Worlds

Record the durable rules in your **World** description or knowledge. Use direct statements such as “Coral songs influence a living island but cannot command it.” Put local exceptions on the relevant **Location** or **Character** instead of making the global rule vague.

## World checkpoint

Choose one ordinary person and one powerful person. Describe how the same rule helps one and burdens the other. If it changes nothing beyond spectacle, give it a cost or consequence.

Next, let the rules become tangible in [Create an Anchor Location](/learn-worldbuilding/create-an-anchor-location/).