Lethean Age World Master Handbook

The World Master Handbook explains how to run the Lethean Age as a tabletop RPG. It should help a World Master present the world, adjudicate ordinary play, build settlements and expeditions, pace revelations, and turn the setting's strange systems into playable situations.

This book is paired with the Setting Handbook. The seam is deliberate. The Setting Handbook holds the content: the true history, the actual nature of the miasma and the Redoubts, the Vril-ya, the Pacific Northwest as canon. The World Master Handbook holds the technique: how to reveal that content a fragment at a time, how to keep the table inside the in-setting view, how to pace, how to adjudicate, how to make the world feel earned. When a section here calls for a piece of setting truth, it cross-references the Setting Handbook rather than reproducing the truth.

This file intentionally starts as a table of contents and migration map. No existing canon has been moved into it yet.

How To Use This Book

Use this handbook for running sessions, preparing adventures, designing settlements, choosing rewards, and deciding what the characters can discover. Use the regulations when a procedure needs exact resolution. Use the Setting Handbook when you need to know what is true in the world (and what your players do not yet know).

Part 1: Running the Lethean Age

Source material:

Setting Handbook Ch. 1 -- Using This Book (the Forgetting as design conceit, voice and register)
rulebooks/0-lore.md sec. 0.8 (tone notes)
rulebooks/6-conflict.md

Draft sections (technique):

Holding dark wonder at the table, not grim nihilism.
Running the gap between what the characters know and what you know.
The Forgetting as a play move: how to refuse to explain.
Scientific romance as table language: substituting Miasm, Winds, and Lattice imagery for fantasy imagery on the fly.
Keeping the world physical, not supernatural, when the players reach for D&D vocabulary.
Treating cargo-cult ritual seriously, neither comic nor sacred.

Part 2: The World As A Place

Source material:

Draft sections (technique):

Presenting real-world geography to players who do not have a globe.
Running biomes as profile shapers, not backdrops.
Running a ruin as spelunking, not urban exploration.
Pacing a Redoubt expedition: outer levels, partial collapses, what to never let the party reach.
The Broken Moon as background detail, not a reveal.
Running miasm-rich and miasm-dead places: when the Miasm is the antagonist.

Part 3: The Wind

The Wind is the moment-to-moment availability of each of the eight miasma colors in a given area. As a World Master you own three things about it: the current level of each color, when a Change happens, and how the Change is resolved.

Setting initial colors

For a region your party is moving through, assign each of the six common colors (red, orange, yellow, green, blue, violet) a starting level from 0 to 9. Black and white are very rare and usually start at 0 unless the location is unusual (see Setting Handbook Ch. 3 -- The Substrate). Higher numbers mean the color is dense; 9 is saturated, 0 is absent.

The baseline is your call. Pick numbers that fit the biome and the moment. A miasm-rich ruin might run 5/4/3/6/2/4; a windswept coast might run 3/3/3/3/4/3 with blue trending up; a miasm-dead irradiated zone might run 0/1/0/1/0/2. There is no need to be statistical -- the players experience the Wind by what they can and cannot cast, not by the numbers on your tracker.

When the Wind Changes

A Change happens when you want one to happen. Typical triggers:

Crossing a substantial regional or biome boundary.
A weather shift or storm front passing through.
An in-world event that should clearly disturb the local Wind profile (an explosion, a Redoubt seal breaking, a relic discharge).
Time pressure: every long rest, every day, every encounter -- whatever cadence suits the campaign.
A character or effect Burns the Wind (see below).

You do not have to Change the Wind on a schedule. A region can hold its profile for an entire session if the situation supports it.

Resolving a Change

Resolve a Change in three steps:

Roll the Strength of the Wind. Roll d10 - 1 for a magnitude from 0 to 9. On 0, the Change registers but nothing actually moves; the Wind held.
Roll direction for each color. For each of the six common colors, roll d3 (or 1d6: 1-2 = rise, 3-4 = hold, 5-6 = fall). Note which colors rolled up, steady, or down. Black and white only roll when the situation warrants it.
Apply the change. See Distributing the change below.

Distributing the change

Let U be the count of colors that rolled up and D the count that rolled down. The amount each rolled color shifts depends on which direction dominates.

Tie (U == D). Every rolled color shifts by 1 in its rolled direction, regardless of Strength. Up colors gain 1, down colors lose 1, steady colors hold.
One side dominates (U ≠ D). Let K = max(U, D). Each up color rises by floor(Strength / K), minimum 1. Each down color falls by floor(Strength / K), minimum 1. Steady colors hold.

Worked examples:

Strength 6, three colors up, zero down. K = 3. Each up color rises by 6 / 3 = 2. Three colors gain 2 levels.
Strength 5, five colors up, zero down. K = 5. Each up color rises by 5 / 5 = 1. Five colors gain 1 level.
Three up, three down (tie), any Strength. All six colors shift by 1 in their rolled direction.

Open question -- confirm distribution rule. The original specification read: "if a magnitude 5 is rolled, and one to five colors roll increase then each increases one." Under the rule above (floor(Strength / K)), Strength 5 with a single up-color yields +5 to that color, not +1. The two clear examples in the spec (Strength 6 with 3 up gives +2 each, and the 3-up / 3-down tie gives +-1 each) align with floor(Strength / K); the Strength-5 / single-color edge case may have been a slip. Confirm at the table whether the rule should be:

(a) floor(Strength / K) (this draft), where a single dominant color can swing several levels in one Change, or
(b) each rolled color always shifts by exactly 1 regardless of Strength, with Strength acting only as a Change-or-no-Change threshold or as a cap on the number of colors that can shift.

After applying changes, clamp every color level to the range [0, 9]. A color cannot rise above 9 or fall below 0 from a single Change.

Burning the Wind

A character or effect can Burn the Wind in a single color (see the Mage's Burn The Wind as the canonical example). The procedure:

Apply the burn's immediate effect (typically resolving a class feature; the Mage's Burn The Wind, for example, treats the burned color as twice its current level for one cast).
Set that color's level to 1.
Immediately resolve a Change of the Wind (see Resolving a Change above). Depending on how the burned color rolls and the Strength, it may fall further to 0, hold at 1, or partially recover.

A Burn does not pre-set other colors' levels for the Change; only the burned color is forced to 1. Subsequent Changes restore the color through ordinary play.

A multi-color Burn (e.g., a high-level Mage burning two or three colors in one cast) sets each named color to 1 and then resolves a single Change. The Change applies to all colors as usual, including the burned ones.

Tracking the Wind at the table

A six-row tracker on a notecard is usually enough: write the six common colors and their current level. Update the values when a Change happens. Tell the players what colors are reachable when they look at their Protocol options, not the exact numbers -- the in-setting view is "the Wind is thin in red right now," not "red is at 1."

Part 4: Settlements And The Law

Source material:

Setting Handbook Ch. 6 -- Project Challenger and The Law
Setting Handbook Ch. 7 -- The Pacific Northwest (Everett as worked example)
rulebooks/7-societies.md

Draft sections (technique):

The Law at the table: how "Are you of the Law?" lands as more than flavor.
Running gate recitations with weight, not as a roll-to-skip.
Running characters who choose to step outside the Law -- the world's response.
Settlement services, repair, rumor, faction contact.
Building a settlement around its Law variant.
Running the Tenfold rite (or a local variant) when a player wants Adventurer status.

Part 5: Factions And Society

Source material:

Setting Handbook Ch. 6 -- Project Challenger and The Law (mental factions, Challenger legacy)
Setting Handbook Ch. 4 -- The Peoples
rulebooks/7-societies.md

Draft sections (technique):

Running mental factions as cognitive discipline, not church membership.
Tracking faction reputation across a campaign.
The Challenger Preparists as a recognizable but never-named faction.
Seeding placeholder factions for a specific campaign without canonizing them.
Guilds and parties as in-faction social structures.
Outlaw networks and the line at outside-the-Law.

Part 6: Relics, Rewards, And Economy

Source material:

Setting Handbook Ch. 7 -- The Pacific Northwest (Verdant Glass, ammunition, Greenhouses)
rulebooks/5-items.md
rulebooks/7-societies.md

Draft sections (technique):

Rewarding portable capability rather than coin.
Running Scrap and Crystals under current Book 7 canon.
Running ammunition, cells, and Verdant Glass as local economies when the campaign goes regional.
Appraisal as a play beat, not a roll.
Building relic quirks the table will remember.
Running Greenhouses when Everett or an Everett-adjacent module is in play.

Part 7: Campaign Structures

Source material:

Setting Handbook (the whole book; this is the section that draws on most of the canon)
rulebooks/0-lore.md
rulebooks/7-societies.md

Draft sections (technique):

Settlement-centered campaigns: how a single enclave becomes a season of play.
Redoubt expeditions: pacing depth, surviving partial collapses, withdrawing.
Trade road campaigns: the wilderness between settlements as the campaign.
Faction campaigns: putting a mental faction at the center of the table.
Pacing the Vril-ya reveal. The truth lives in Setting Handbook Ch. 4; what belongs here is the schedule on which fragments arrive at the table.
Everett as a starter module: where to begin a fresh table on the Tenfold rite.

Part 8: Adjudication Guidance

Source material:

rulebooks/3-apocalyptia.md
rulebooks/4-characters.md
rulebooks/5-items.md
rulebooks/6-conflict.md

Draft sections (technique):

Calling for ability checks when the outcome matters.
Combat pacing: when to slow down, when to skip a round.
Environmental danger as a session-shaping force, not a save-or-die.
Mutation consequences played for character, not punishment.
Relic failure and partial success: when a Seed almost works.
When to use exact regulations and when to keep play moving.

Review Notes

The Setting Handbook is the spoiler-containing book. Cross-link to it freely; do not reproduce its content here. Anything player-safe that needs to live in two places is duplicated by mistake.
Keep hidden history hidden from player-facing material. The truth lives in the Setting Handbook.
Make cargo-cult engineering serious, not comic.
Avoid nostalgia for the old world. Nobody at the table is allowed to mourn a civilization no one remembers.
Treat Redoubts, miasma, mutations, and relics as physical phenomena with incomplete understanding -- not as the supernatural.