Worldbuilding is one of the pillars of a coherent universe in fantasy and isekai. Building a believable world does not mean explaining everything, but establishing structuring rules, a stable internal logic, and invisible decisions that can support the story over time.
In this article, I am not describing a specific universe. I am presenting a way of thinking about worldbuilding so that it remains coherent, flexible, and narratively sustainable.
I. Start with the World, Not the Rules
Before systems, before powers, before even plotlines, there is one fundamental element: the world must exist as a concrete space.
In my case, the first step was not writing rules, but drawing the world. I relied on imaginary maps, medieval-style geographies, and plausible terrain — not to define everything, but to give the universe spatial credibility.
I used world-building tools to design continents, oceans, forests, terrain, and climate zones. This visual work is not meant to illustrate the story, but to impose implicit constraints on the narrative.
Why does this matter?
Because geography naturally imposes:
- distances to travel,
- borders to cross or defend,
- isolated or tense regions,
- strategic routes and chokepoints.
Even in a fictional universe, these constraints prevent arbitrariness. They create a logical framework in which events make sense.
Concrete example
If two cities are separated by a mountain range, a conflict cannot be resolved in a matter of hours. The terrain alone imposes time, risk, and difficult choices — without ever needing explicit explanation.
II. Avoid Freezing Systems Too Early
One of the most common pitfalls of worldbuilding is trying to define everything from the very beginning: magic rules, classifications, exceptions, hierarchies.
I realized fairly early that this approach leads to narrative confinement: every rule defined too early reduces future freedom and increases the risk of contradictions.
In my case, I applied a simple rule: in the absence of magic, the physical laws of the world follow those of our own. This provided a stable foundation without locking every system into place.
Fictional example
If an author decides in the very first chapter that fire magic never works in the rain, they may eliminate a powerful scene in which a desperate, soaked mage tries anyway to ignite a flame to save a wounded companion. A rule frozen too early can kill a scene before it exists.
Powers therefore remained deliberately broad and flexible — not due to vagueness, but to preserve narrative adaptability.
There was a clear intention: for example, two forms of magic capable of opposing or complementing each other in specific contexts, without defining every interaction from the start.
The distinction is crucial:
- a rule defined too early rigidifies the story;
- a structural intention guides writing without constraining it.
Systems should not precede the story. They should emerge when the narrative requires them, within an already coherent framework.
Imagination unfolds at the edges of narrative progression. In other words, event C becomes conceivable only because event B has already occurred.
As the story advances, a universe of possibilities gradually opens. What was inconceivable at the beginning becomes plausible later — not because the author improvises, but because the world has already established the conditions that make these possibilities visible. One must move forward to see them.
Fictional example
If a character can manipulate light, I do not immediately define every limitation. I only know that light cannot be created ex nihilo. This single constraint prevents early excess while leaving room for believable evolution.
III. Everything That Influences the Plot Must Be Framed
Here is one rule I consider non-negotiable: everything that directly affects the plot must be framed.
This does not mean everything must be explained to the reader. It means nothing is left to chance from the author’s perspective.
An element may remain implicit or suggested, provided it rests on a solid structure.
To maintain this stability, I rely on:
- a precise chronology,
- characters’ ages at key moments,
- past relationships,
- causes and consequences of decisions.
Even when an explanation never appears in the story, it exists upstream.
Ambiguity is narrative, never structural.
Concrete example
If a character refuses to act at a critical moment, that decision is rooted in a specific past experience, even if the reader never sees it.
Mini-Method — Avoid Premature Locking
Before fixing a rule, I ask myself three questions:
- Does this element directly affect the plot?
→ If yes, it must be framed. - Do I need this rule now or later?
→ If later, I leave it open. - Does this rule increase my narrative freedom or reduce it?
→ If it restricts the story, it is premature.
IV. Reject Easy Solutions
Rejecting Deus Ex Machina implies a clear responsibility: accepting the consequences of established rules.
When facing an apparently impossible situation, I step back. I explore multiple hypotheses, test their plausibility, sometimes by comparing them to real historical or human situations.
If no solution truly holds, the conclusion becomes unavoidable: the character fails.
Conversely, inventing a power or rule solely to escape a dead end immediately weakens the credibility of the universe. Readers instinctively sense this logical rupture, even when the scene is spectacular.
A solid world is not one where everything works out, but one where every outcome has a cost.
V. Deliberately Leaving Areas Unexplored
Defining everything too early creates another form of rigidity.
Naming every country, explaining every origin, establishing every diplomatic relationship from the outset often artificially narrows narrative space.
For instance, when writing The Otherworlder’s Heir, it was not necessary to define every country or the full way of life of the Kembari continent. It was enough to describe the places the characters actually travel through.
Leaving areas unexplored allows:
- future plotlines to emerge,
- adaptation to characters’ psychological evolution,
- avoidance of the author’s logic overpowering that of the characters.
Some explanations will appear much later. Others will never appear in the books, while still existing elsewhere.
Not saying everything does not mean nothing was decided.
It means consciously choosing when and where to reveal.
Conclusion — A Solid Universe Is a Thought-Out One
Good worldbuilding is not built on accumulating information, but on the quality of invisible decisions.
Readers do not need to know everything to feel coherence. They instinctively sense when a world stands on solid ground.
Building a coherent universe means accepting:
- setting rules without exposing them,
- preserving margins without losing control,
- rejecting easy solutions,
- and trusting internal logic over immediate effect.
In fantasy and isekai alike, imagination works best when supported by a solid structure, even when that structure remains out of sight.