#Yoma Core Economy

Contents

Campaign Module — ex1 domain and Barrier resource rule. In the core book, yoma cores exist only at the level of plot hooks(Kunitomo Guild, Hannya ritual). This supplement defines cores as a standardized resource, making the cycle of harvest, storage, spoilage, processing, and consumption the backbone of Barrier maintenance and domain operation.

Core References

- Required: Yoma Bestiary · Non-Combat Checks

- Reference: Autonomous Automaton Research · Hannya Ritual

- In this supplement: Barrier System · Domain Facilities

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#Scent — What Is A Core?

A yoma core is crystallized obsession.

When a yoma was a person, or a person's shadow, or accumulated grudge — the hardest thing at the center of that existence condenses. That is the core. It is not a heart and not a soul. It is something between them. It can be pulled out at the moment the yoma dies; if it is not pulled out, it scatters with the corpse.

It is warm in the hand. A little below human warmth. A very low vibration climbs from palm to elbow. They say your palm lines change if you hold one too long. No one asks whether that is true.

Cores naturally vary according to yoma ranks such as Minion, Veteran, Elite, and Lord, but when used as a domain resource, only 3 stages are used.

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#Law — The 3 Core Stages

Mob-grade yoma cannot yield cores. Record harvestable cores in the 3 stages below.

Rank conversion principles:

• Cores from Minion- and Veteran-grade yoma are all recorded as unstable cores.
• Cores from Elite-grade yoma are recorded as stable cores.
• Cores from Lord-grade yoma are recorded as high-purity cores.
• If a core drops by 1 stage, process it in the order high-purity → stable → unstable → spoiled(invalid).

#Additional Rule For Harvesting Large Yoma Cores

Elite- and Lord-grade yoma have cores lodged deep within them, so they can be harvested only within 5 rounds immediately after the enemy is defeated. After that, the spirit body wraps around the core and scatters.

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#Harvest Check

Immediately after defeating a yoma, make a check to remove its core.

Harvest check:
 2d10 + Wisdom + highest proficiency among Herbalism, Medicine, or Exorcism >= Target Number

Results:

• Success: gain the core.
• Failure: core damaged. Gain a core 1 stage lower. An unstable core spoils and becomes invalid.
• Critical Hit(double + success): gain the core + add +1 to this week's weekly spoilage event.
• Fumble(double + failure): core destroyed. Harvest fails.
• Heavenly Mandate(10-10): core + 1 fragment of the yoma's last memory.
• Karmic Retribution(1-1): core destroyed + harvester loses 1 Wounds.

#Target Number modifiers

The character with the skill makes the harvest check. If a character without the skill attempts it, Target Number +3. Herbalism, Medicine, and Exorcism are the representative skills; onmyoji and shugenja receive a baseline +1 modifier.

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#Storage — Weekly Spoilage Event

Harvested cores spoil if they are not used immediately. However, do not roll d100 or track storage weeks for each individual core. Every Sunday, process the weekly spoilage event only once together with the Barrier maintenance check.

#Weekly Spoilage Event

If there is at least 1 core in stock, roll d10 + storage modifier.

If there are no high-purity/stable cores, determine the number of unstable cores that spoil with d10.

#Exceeding Storage Limits

If storage exceeds the limit, immediately drop the oldest cores by 1 stage equal to the excess. If an unstable core drops, it spoils and becomes invalid.

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#Consumption — Barrier Injection

Injecting a core into the Barrier is a ritual led by the onmyoji.

Batch injection: In the same ritual, up to 3 cores of the same stage can be injected together. Ritual time is based on the highest stage, plus 10 minutes per additional core. High-purity cores are always injected alone.

Casters other than the onmyoji:

• If there is a shrine assistant instructor NPC, they can inject unstable cores instead. Efficiency is 50%(Barrier HP +5).
• PCs with shugenja or onmyoji skills can also do this. Efficiency is 50%.

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#Processing — Core Transformation

#Core Synthesis

• Condition: 3 cores of the same stage → 1 core of the next higher stage
• Success rate: 2d10 + Wisdom + Herbalism >= 15
• Success: gain 1 core of the next higher stage
• Failure: lose 1 material core
• Critical failure(1-1): all materials spoil
• Unlock: shrine upgrade "core synthesis altar" (→ 01-05)

#Refinement

• Condition: 1 core → 1 pure spirit-vein crystal(separate resource)
• Use: masterwork weapon modification, medicinal crafting, etc.
• Unlock: after upgrading an outsider NPC laboratory

#Crushing

• Condition: 1 core → d10 core fragments
• Use: Barrier bullets(special teppo ammunition), one-use weapon enhancement
• Recovery effect: 1 core fragment = Barrier HP +1

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#Emergency Uses For Cores

#Emergency Healing

• Crush 1 unstable core → emergency healing ritual → 1 incapacitated character recovers +1 Wounds
• Condition: presided over by a monk or physician NPC
• Side effect: patient gains Spirit Realm Exposure +1

#Weapon Enhancement

• 1 unstable core + masterwork weapon → attack +1 for 1 combat(core destroyed)
• 1 stable core + masterwork weapon → [Pierce all] 1 time on the first Critical Hit during 1 combat

#Ritual Offering

• Can be used as a gift during yoma negotiation(negotiation Target Number -3)
• Effective on specific intelligent yoma after Chapter 4(Spirit Realm Intelligences)

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#Weekly Core Balance Simulations

#Model — "A Smooth Week"

Monday morning: Barrier HP 60, core stock unstable 3·stable 1
Monday~Friday: 2 expeditions, 4 unstable cores additionally harvested
Saturday afternoon: Barrier injection ritual — unstable 3 + stable 1 = Barrier HP +60
Sunday night: Barrier maintenance check succeeds, Barrier HP natural -3, weekly spoilage event stable
Result: Barrier HP 60 +60 -3 = 117, core stock unstable 4

#Model — "Core Shortage Crisis"

Monday: Barrier HP 45, stock 0
Monday~Friday: 1 failure out of 2 possible expeditions
Saturday: remaining PCs depart urgently, gain only 1 unstable core
Sunday: Barrier HP 45 +10 -3 = 52
→ enter danger range if core shortage continues for 2 consecutive weeks

#Model — "Night Of The Barrier Crisis"

Barrier HP enters 20 → side [Night Of The Barrier Crisis] force-triggers
→ 1 Lord-grade yoma attempts breakthrough → Barrier HP -15
→ on success: gain high-purity core → Barrier HP +60
→ on failure: Barrier HP 0 → ending

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#Sheet Format — For GM Tracking

[Core Stock Sheet]
This week: week ___

In storage:
 unstable cores: ___
 stable cores: ___
 high-purity cores: ___

This week's harvest:
 unstable: __ (source: ___)
 stable: __
 high-purity: __

This week's injection:
 unstable __ cores → Barrier HP +__
 stable __ cores → Barrier HP +__
 high-purity __ cores → Barrier HP +__

Weekly spoilage event:
 storage environment: ___ / roll: ___ / result: ___

Special notes: ___

For the dedicated sheet, see 80-03-core-economy-tracker.md.

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#Design Advice — For The GM

1. Check stock once every session: "How many cores do we have left?" should become a player operations decision.
2. Always roll the weekly spoilage event: instead of tracking each individual core, one weekly event carries the tension.
3. Do not be stingy with failed checks: a stage drop on harvest failure makes preparation and assistance valuable.
4. Treat high-purity cores as treasure: Lord-grade yoma and high-purity cores should usually be saved as climax rewards.

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#Connected New Rules

• Barrier System — the main use for cores
• Domain Upgrades — storage and core synthesis facilities
• Onmyoji NPC — caster for injection rituals
• Morale — core shortage → resident morale drops

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"Warmth in the hand is not proof of the living. It is memory of the dead." — Hoshino Gensho, handing the first core to a young PC.