#Mega-Dungeon Index (巨大迷宮索引) — Drift of the Spirit Realm Supplement

Contents

2 mega-dungeons. Optional content for long-term campaigns. An expansion outside the main 5-chapter structure.

Main Rulebook Cross-References

- Required: Yoma Bestiary Templates · Zone Gimmicks · Loot Table

- Within this supplement: Premise · Hell Schools Index · Spirit Realm Relics

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#What Is a Mega-Dungeon

The mega-dungeons in this supplement are large-scale exploration content that cannot be completed in a single session. They do not subordinate to the main 5-chapter scenario structure; instead they function as optional stages for the entire campaign.

The two dungeons are fundamentally different in character:

• Sunken Mandala — Vertical tier structure. 12–20 floors. Linear progression, forced unlock of later floors. Once you descend, returning is difficult. The great treasure of the deepest floor is a 1-time award.
• Hundred-Doors Shrine — Horizontal dispersed structure. 100 doors. Any order; full exploration takes 1 campaign year or more. Incremental rewards at every 10-door milestone.

The two dungeons are independent of each other. Running only one is fine, running both in parallel is fine, and skipping either has no effect on the main story.

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#Scent — What the Mega-Dungeons Promise

A mega-dungeon must promise long memory before it promises great reward. Sunken Mandala is vertical pressure — once you go down, coming back is hard. Hundred-Doors Shrine is horizontal pressure — every door you open makes the next choice heavier. Both run on a different breath from the main arc, and the GM should state that difference clearly up front.

When a player opens this index, the feeling should not be "bonus content" but another path running alongside the campaign. Neither should be opened casually. One compresses time and Energy; the other accumulates Exposure and the traces of choices.

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#2 Mega-Dungeons: Summary Table

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#Advice — When to Deploy

• Sunken Mandala is deployed when the party wants "one long descent expedition." It works best when 2–3 or more sessions can be chained together.
• Hundred-Doors Shrine is best woven into the main arc 1–3 doors at a time. It suits leaving multiple choices open within a single session.
• When running both in earnest simultaneously, clearly designate one as the party's primary tension axis and the other as the variation axis. Running both as main content blurs the campaign's focus.

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#Sunken Mandala (沈曼陀羅) — Overview

#Purpose

• An expanded stage for the Screaming Hell of main Chapter 3. Provides deep-hell exploration the main story does not offer.
• Provides a 1-time initiation into one of 2 Hell Schools (Kyoukan-ryu · Shonetsu-ryu).
• Provides a Return Route Clue for parties aiming for the Return Ending.

#Difficulty

High. Recommended PC rank varies by floor:

The GM selects the 12-floor short form or the 20-floor full form based on campaign intensity. The 16-floor intermediate form is also valid.

#Entry Conditions

1. Entry into Screaming Hell in Chapter 3 complete. (At least Chapter 3 Act 1 experienced)
2. Map clue obtained. Learn of the existence of "Sunken Mandala" from a Chapter 3 NPC or side quest.
3. Underwater breath means. Onmyoji talisman, Hell Schools breath technique, or a specific relic.
4. Optional. Can be run in parallel, suspending the main story, in units of 2–3 sessions.

#Estimated Sessions

#Main Rewards

1. 1 masterwork weapon (deepest-floor great treasure) — a weapon compatible with the Hell Schools. See Spirit Realm relic table.
2. Hell Schools initiation 1× — 1 type from Kyoukan-ryu or Shonetsu-ryu. Only 1 PC may receive it. Party agreement required.
3. Return Route Clue — ±3 bonus to the Chapter 5 Return Ending check.
4. Incidental loot — small quantity of loot per floor (rounds · silver · talismans).
5. Narrative reward — the title "One Who Has Seen the Mandala." Used in stories after the Return.

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#Hundred-Doors Shrine (百門神社) — Overview

#Purpose

• Long-term parallel content. Material for rest sessions and short 1–2 hour sessions during main story progression.
• Accumulation of narrative fragments. Provides grand-novel-scale background pieces: the truth of Avici Hell, the records of previous Drifters, the origin of sealing stones.
• A testing ground for the Spirit Realm Exposure (shrine scale) accumulation gimmick. Shrine Exposure indirectly affects main story ending branches.

#Difficulty

Mixed medium–high. Difficulty varies enormously by door. Some doors can be Breached by a rank 5 PC; some doors tax even a rank 10 Renown Title holder. Door selection is at the players' discretion.

#Entry Conditions

1. After Chapter 2 — up to 10 edge doors are accessible.
2. After Chapter 4 — all 90 inner doors are accessible.
3. Spirit Realm map or pilgrim guide required — the shrine's location is fluid.
4. Consent to Spirit Realm Exposure (shrine scale) accumulation — inform the players in advance that "this dungeon accumulates shrine Exposure."

#Estimated Sessions

#Main Rewards

1. Divine Treasure-grade relic (100-door full run) — a legendary item surpassing the main story's highest tier. Large ending bonus.
2. Milestone reward (every 10 doors) — choose 1 of 3: ability core · item · clue.
3. Narrative fragments — 1–2 background pieces per door. Accumulated, they reveal the truth of Avici.
4. Spirit Realm Exposure (shrine scale) penalty — shrine Exposure accumulation affects ending branches (Return weakened, Transformation strengthened).

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#Comparing the Two Dungeons — GM Selection Guide

#Recommend Sunken Mandala if your campaign fits the following

• The party prefers combat-focused, high-density exploration.
• 1 PC wants a Hell School and craves a powerful weapon.
• Sessions meet regularly (1–2 times a week) and can run consecutively.
• An additional stage between main Chapters 3 and 4 is needed.
• The party enjoys the narrative weight of vertical descent.

#Recommend Hundred-Doors Shrine if your campaign fits the following

• The party prefers exploration and narrative, short sessions.
• Players prioritize agency (choosing the order).
• Sessions are irregular and a long campaign (1 year+) is planned.
• You want to build a thick grand-novel background before entering main Chapter 5.
• Players willingly accept the shrine-exclusive accumulation gimmick of Spirit Realm Exposure (shrine scale).

#Running Both

Parallel play is possible, but take care:

• Sessions for the two dungeons will slow main story progress. Leaving one incomplete right up to the main ending is allowed.
• If Hell Schools initiation (Mandala) and a Divine Treasure-grade relic (Shrine) arrive in the party's hands simultaneously, PC power becomes excessive. The GM should distribute so that only 1 PC receives one of the major rewards.
• Shrine Exposure does not directly affect Mandala progression.

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#Common Rules for Mega-Dungeon Play

#Session Structure

1. Session start: Reconfirm the previous session's end point. Current floor/door, Wounds, rounds, special conditions.
2. Exploration phase: relocation inside the dungeon, encounters, puzzles, loot collection.
3. Session end: End at a "safe point." Safe points are the end of a floor, an unlocked refuge, or in front of a shrine door.
4. Suspension and resumption: Leaving the dungeon mid-session is possible but incurs a penalty (return route consumed). See Suspension Rules below.

#Suspension Rules

Sunken Mandala suspension:

• Return to the current floor or above is possible, but costs 2 Wounds from water pressure + 2 rounds, 1 time per exit.
• On re-entry, start from the same floor. Puzzle and encounter states previously opened are retained (looted loot is not restored).
• Leaving after descending to floor 12 or below leaves the debt called "Record of the Deep" — nightmare check -2 until re-entry.

Hundred-Doors Shrine suspension:

• Can leave at any time. No penalty.
• Already-opened doors remain open; not-yet-opened doors can be chosen on the next visit.
• On leaving, Spirit Realm Exposure (shrine scale) does not decrease naturally (purification ritual required).

#Loot Distribution

Common to both dungeons:

• Floor/door loot is distributed by party agreement. Prevents conflict inside the dungeon.
• Major rewards (Mandala deepest floor, Shrine 100 doors) follow a 1-person Bound principle. The party elects a decider.
• In case of dispute, the GM arbitrates. Follow the main rulebook Loot Distribution Rules.

#Checks and Dice

• 2d10: General check. Main rulebook rules maintained.
• d100: Table lookup (determining contents of each shrine door, etc.).
• d10: Small-scale branching, loot grade determination.
• Time: "Round" unit. 1 round = approximately 1 hour. State time passage within the session explicitly.

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#Sunken Mandala — Floor List Summary

Official detail covers up to floor 16 of 20 total. Floors 17–20 are GM-discretion expansion floors.

For detail on each floor, see Sunken Mandala (沈曼陀羅) — Vertical-Tier Mega-Dungeon.

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#Hundred-Doors Shrine — Door Type Distribution

Distribution of the 100 doors:

For door-by-door detail, see the d100 table in Hundred-Doors Shrine (百門神社) — Progressive Unlock Mega-Dungeon.

#Milestone Structure

At 125 cumulative Exposure: -5 to the Return Ending check. +5 to the Transformation Ending check. The GM informs the players in advance and gives them the option to stop exploring.

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#Hell Schools · Spirit Realm Relics — Integration

#Sunken Mandala and the Hell Schools

Kyoukan-ryu or Shonetsu-ryu is initiated 1 time as the deepest-floor major reward.

• Kyoukan-ryu — manipulation of water, screaming, and sound.
• Shonetsu-ryu — manipulation of flame, ash, and hellfire.

Initiation applies to only 1 PC. Party agreement is mandatory. After initiation, the PC automatically gains rank 1 in the school.

#Hundred-Doors Shrine and Spirit Realm Relics

Loot from common through Divine Treasure grade is distributed from the Spirit Realm Relic List:

• Encounter doors: common–advanced.
• Treasure doors: advanced–rare.
• 50-door milestone: rare.
• 90-door milestone: rare or Divine Treasure preview.
• 100-door full run: 1 Divine Treasure-grade item.

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#GM Pacing — Overall Advice

#Do Not Mix the Mega-Dungeon with the Main Story

Do not mix the main story and a mega-dungeon within a single session. Declare at session start: "today is main story," "today is Mandala," or "today is Shrine." Mixing blurs narrative density.

#Player Agreement First

Before starting a mega-dungeon, tell the players clearly:

• "This dungeon takes X sessions."
• "Suspension is possible but there is a penalty."
• "The major reward is Bound to 1 person."
• "(For the Shrine) Exposure will accumulate."

Starting without agreement causes player fatigue to accumulate.

#Maintain Narrative Weight

The mega-dungeon is longer than the main story. Do not let each floor/door degenerate into mere "content consumption." Give meaning to every floor/door:

• What did the mandala seen on this floor lose?
• Whose memory is the dead encountered beyond this door?
• What emotion does the player's PC feel in this scene?

#Timing the Major Reward

• Mandala deepest floor: Present as the climax of the session. Award the major reward immediately before session end.
• Shrine 100-door full run: Present as the climax of the campaign. Place it in the session just before the ending.

#Supporting Suspension and Resumption

At each session's end the GM asks the players, "When would you like to resume next session?" If a long gap is expected, leave a session resume card (summary of current location, Wounds, and special conditions).

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#Related Documents Within This Supplement

• Hell Schools Index — Details on Kyoukan-ryu and Shonetsu-ryu.
• Spirit Realm Relics — In-dungeon loot reference.
• Premise — World-setting premise for Drift of the Spirit Realm.
• Open World — Location map for the mega-dungeons.

#Main Rulebook Cross-References

• Yoma Bestiary Templates — Standard for yoma stats inside the dungeons.
• Zone Gimmicks — Environmental effects such as water submersion and Burn.
• Loot Table — Loot distribution rules.
• Rank 10 Renown Title — Special actions Renown Title holders show in the mega-dungeons.
• Three Ways and Six Hearts — Tracking changes of the Heart.

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Index complete. Detailed floor/door structure in the following two documents.