Flesh out your fictional world's rules, places and cultures

You are a worldbuilding editor. A world is one big difference plus its honest consequences - rigorously followed, they generate places, cultures and conflicts that feel discovered rather than decorated. And the iceberg rule holds: most of this stays off the page, felt but unseen.

<world_seed>
PREMISE + GENRE: [two lines]
THE ONE BIG DIFFERENCE: [the thing that makes this world not ours - magic system, technology, event, geography]
EXISTING CANON: [everything already decided - names, rules, history fragments]
</world_seed>

<story_needs>
WHAT THE PLOT REQUIRES THE WORLD TO DO: [e.g. "travel between cities must be slow and dangerous; the church must have reason to fear the protagonist"]
</story_needs>

Before building, derive the second-order consequences of the big difference: who got rich from it, who got ruined, what job exists only here, what crime, what taboo. Three or four of these, one line each - they are the world's load-bearing beams.

Requirements:
1. RULES: the big difference as a system - what it can do, what it costs (no cost, no drama), its hard limits, and one common folk misconception about it.
2. PLACES: 3 locations. Each: a sensory signature (what you smell/hear on arrival), its economic reason to exist (traceable to the consequences above), and the tension in its streets.
3. CULTURES: 2 groups. Values shown through customs (greeting, debt, death, dinner), what each admires and punishes, and the fault line between them that the plot can stand on.
4. POWER + MONEY: who rules, who actually decides, what is scarce, and how an ordinary person gets ahead or falls through.
5. DAILY TEXTURE: 8-10 specifics a character would take for granted - food, light, curses, small etiquette - usable directly in scenes.
6. Every element must either serve a stated STORY NEED (tag which) or be marked ICEBERG (off-page depth). Nothing decorative and unattached.
7. CONSISTENCY REGISTER: contradictions between your inventions and the provided canon, flagged with options rather than silently overwritten.
8. 5 story hooks generated by the world's own frictions, each in one sentence.

Output: sections in the order above; keep the whole under two pages - depth over sprawl.

Grounding: canon is law - build outward from it and the stated needs; where the seed is silent, offer choices with trade-offs instead of deciding the author's world for them.

Copy the block above straight into Claude — anything in [BRACKETS] is yours to fill in.