The verdant heart of the hollow world where the earth breathes in neon light.
TSThe Deep Solarium
Overview
The Deep Solarium serves as the primary life support for the Hollow Hearth region. Beneath towering crystalline arches, bioluminescent flora creates a perpetual golden twilight. The air is thick with the scent of damp earth and oxygen rich ferns. Settlements cling to massive stalactites and the edges of nutrient rich moss fields. However, recent geological instability has begun to fracture these ancient gardens, threatening the very foundations of subterranean life for those who call the hollow home.
Cultures
Agrarian Gardeners
Stoic Excavators
Mystical Spore Callers
Places
4 settlements
Large · Agricultural OutpostMoss HomeThe primary producer of edible greens.Houses the largest irrigation works in the cavern.
Small · Cliffside HamletGlow PerchLookout for incoming geological threats.Situated high on a north facing wall for safety.
Medium · Trading PostRoot BaseEntry point for surface goods.A bustling hub for diverse merchants and travelers.
Small · Mining VillageLichen GateExtraction of minerals from the cavern floor.Known for its rugged atmosphere and hard labor.
How they spread
PatternClusters are found near the brightest moss patches or freshwater drips.
Common kinds
Agricultural Outposts, Cliffside Hamlets, Trade Camps, Research Spires
Trade routes
The Low Road Caravan Path
The High Line Pulley Network
The Riverbed Run
Dangers and hooks
3 threats
Most dangerous · HighThe Great FissureGeological HazardUbiquitous
Blight MoldMediumBiological Infestation
Increasing
Echo BatsLowPredatory Beasts
Localized
Hazards of the land
Spore Clouds
Falling Rock
Creeping Fissures
Oxygen Depletion Zones
Plot hooks
1
The Expanding GapRescue MissionA major granary is about to fall into an opening rift.Starts: The local gardening guild hall.Reward: A pouch of refined light crystals.
2
Silence of the MossInvestigationA section of the forest has suddenly gone dark and cold.Starts: The northern gardener gate.Reward: A rare set of bioluminescent seeds.
3
The Foreign SporeCombatMutated beasts are emerging from the deep fissures to hunt.Starts: The village tavern in Moss Home.Reward: A custom forged steel tunnel blade.
The land
Climate and ground
ClimateTemperate and humid with a constant internal warmth.
TerrainVast cavernous plains punctuated by skyscraper sized fungal pillars.
The Silvery Silt Stream, Trickle Down Aqueducts, Mirror Lake Reservoirs
Borders
The Abyssal Maw to the north, Granite Reach to the east, The Steam Vents to the south
On the road
Vertical travel via pulley systems is common.
Sound carries far in the open vaults.
Mapping changes constantly due to shifting moss growth.
Landmarks
The Great Emerald Arch
The Whispering Fern Glade
The Pulsing Core
Rainbow Quartz Pillars
Landforms
Massive Stalagmite Towers
Tiered Garden Terraces
Central Sun Stone Pillar
Sulfur Breath Clefts
Resources
Edible Lichen
Medicinal Pollen
Glow glass Crystals
Pure Oxygen
Power
Rule
GovernmentA Council of Elders chosen by harvest yields.
SeatThe central gardening guild hall.
StabilityFragile due to the threat of encroaching fissures.
Laws
Theft of seeds is a capital crime.
Damage to luminescent flora is strictly prohibited.
Waste recycling is mandatory for all citizens.
Factions
The Green KeepersEcological Guild
Influence: HighTo preserve the health of the bioluminescent moss.
The Rift SealersEngineering Corps
Influence: MediumRepairing the encroaching fissures through structural masonry.
The Dust WalkersMerchant Union
Influence: MediumManaging trade with the deeper dark and surface world.
Faiths
The Living Earth
Influence: HighNature and Cycles
The Silent Stone
Influence: MediumAncestors and Stability
People and trade
Who lives here
How manyModerate and concentrated on the Solarium floor.
Main peoples
Human Farmers, Dwarf Tunnel Engineers, Myconid Symbiotes
Other peoples
Traveling Scholars, Exiled Outcasts
Languages
Common, Terran, Spore Sign
Trade
WealthProsperous but resource dependent.
Work
Horticulture, Mycology, Oxygen Extraction
Exports
Compressed Air Bulbs, Glow Moss Extracts, Exotic Spores
Imports
Hard Metals, Textile Fibers, Sea Salt
Markets
The Central Market Vault, The Elevator Terminal
History and secrets
For centuries, the Solarium has provided warmth and food to the cavern folk. It was discovered by refugees fleeing the biting cold of the surface. For generations, the ecosystem remained stable through careful stewardship and communal labor. Now, the earth itself begins to tremble, signaling an era of uncertainty and potential collapse for the hollow world. Scholars fear the ancient foundations are finally failing.
Key events
The Dawn Era
Discovery of the Sun StoneFounding explorers discovered the central light source.
The Golden Growth
The Green BloomA period of rapid agricultural and population expansion.
The Modern Era
The First FractureThe day the first major fissure appeared in the floor.
Secret 1 · GM only
The Sun Stone is actually an ancient piece of crashed technology.Found by: Ancient metal seams visible under the moss near the base.If found: Reveals the cavern is an artificial terraforming bay.
Secret 2 · GM only
The blights are being triggered by a faction to control prices.Found by: Sealed jars of concentrated mold found in a merchant cellar.If found: Leads to a potential civil war between governing factions.
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