The Underground River

Natural passages (halls and tortured paths). River channel (rushing, cold). Five pools (nigh-bottomless, bright hues).

• Plumb the pools: Heavy carvings in antiquated styles. 1d4-1 in each pool, 1d6 turns to fish out, 1d6*50gp each, attracts random cave fish.
• Dive into pools: CON check to hold breath long enough to reveal Drowned Chambers. 50% chance of lurking cave fish (as giant rockfish). Pring An elegant short sword from a fairy time. It glows pink when fishy folk are near. Enchanted +1, +2 vs fish.

Initial Exploration

Mineral Vents

Sulfurous feeder streams (colourful, pungent). Burbling springs (hot, fizzing). Muddy maw (dribbling, rank).

• Soothing bath: 1d4 turns. Removes 1 disease or restores 1d6hp.
• Investigate muddy maw: Glutinous mud, dribbling oozes (harmless), scattered coinsized electric dragon scales (150 in total, gather 3d20 per turn, 10gp each). Reveals Dragon’s Nursery.

Further Exploration

Drowned Chambers

Mineralized village (Glab-Glab, deep colourful waters). Air chamber (wisp glitter).

• Pilfer village: Requires ability to breathe underwater or repeated dives. 2d4 advanced weapons and tools (100gp each), disturbs 1d4 lurking cave fish (page 10).
• Swim to air chamber: Forest petrified into sparkling agate. Cave wisps (page 10) flicker among ancient ruins (originally built above ground). Reveals Steaming Waterfall.

Steaming Waterfall (Hidden)

Warm water (spray, mineral rich, echoing). Carved handholds (slick, slimy).

• Behind waterfall: Last Glab-Glab creche. Sleeping servant machine (as 6HD bone golem, can be harmed by mundane attacks, but damage is halved) surrounded by small skeletons. If party listens to golem’s sad story (1d6+1 turns), it digs Pring out of its hiding spot and gifts it.
• Climb up waterfall: 50’ climb, 1d6 bitter crabs (as giant crab), reveals Dragon’s Nursery.

Dragon’s Nursery (Hidden)

Subterranean swamp (loam, travertine pans, cave flora). Dripstone pillars (slick, luminous spores). Cave wisps (blue). Stone-encrusted dragon skeleton (100’ long). Waterfall (disappears into an abyss).

• The marvelous skeleton: Scattered dragon scales and horns (120 total, gather 3d20 per turn, 10gp each). A rivulet of holy water runs from beneath the skull (1 vial’s worth per turn). Visitors who stop to examine the skeleton are blessed (as spell). Each turn there is a 1-in-6 chance of attracting 2d4 corrupted dragon spawn (as giant weasel).
• Follow wisps or holy water: 1d4 turns, leads to a natural stone bath filled with holy water and cave pearls.
• In the bath: Coin-sized cave pearls (80 total, gather 2d20 per turn, 50gp each) are food for three tiny electric-blue sky dragon hatchlings hiding within. The eyeless hatchlings cannot survive outside of holy water. It will take 25 years for the hatchlings to grow dog-sized and capable of hunting their own food and surviving outside of holy water. Till then, they must lick one cave pearl per year or starve. Without a pearl, a hatchling starves in 1d4 days. Every hatchling death summons a massive electrical storm to the land above as the sky itself mourns the death of one of its beloved little spirits. The storm wreaks devastation, destroying every tenth living creature and building in a 1 league radius.
• Climb down waterfall: Reveals Steaming Waterfall. Dreadfully tight, wet, rubble.

Regional Challenges

6. Corrupted dragon spawn: 1d4 10’ long amphibious creatures with sucking mouths (as giant weasel). 7. Flooded passage: Unencumbered characters: CON check to swim through without drowning. Attach rope to make passable without check or 2d6 turns to find alternate route. 8. Vertical chimney: 50’ high. DEX check to climb (attach rope to make scalable without check) or 2d6 turns to chisel steps. 9. Walking waterwights: 1d4 waterwights (page 11) begin silently trailing the party, waiting for an opportunity. 1-in-6 chance to notice per watch.

Collapse

1. Mud gushes from the mineral vents. All water becomes turbid. Movement slowed by 30’. +d6 to collapse checks. 2. Burbling, hot, muddy water begins to flood the way forward. PCs must cross a 60’ flow or spend 2d6 turns finding an alternate route. +d6 to collapse checks. 3. Boiling waters begin filling the region. Party may safely return to the path they entered from, or (if protected from intense heat) attempt traversal; PCs must cross a 120’ flow. Afterwards, the region is shut. Path to Chiselled paths and bridges along the dark river.