Two D100 Random Sword & Sorcery Underdark & Underground Encounters Table For Castles & Crusades Campaigns

 This d100 table is designed for the high-adventure, "siege engine" style of Castles & Crusades, blending classic dungeon crawling with the eerie, atmospheric tension of the deep earth. This blog post continues from 

Two D100 Sword & Sorcery sewer & dungeon encounter tables For Castles & Crusades Campaigns

Underdark & Underground Encounters (d100)

d100	Encounter	Details / C&C Note
01–05	1d6 Stirges	Hungrily clinging to the ceiling of a narrow crawlway.
06–10	2d4 Goblins	Scouts looking for easy prey; likely have a pit trap nearby.
11–14	1d4 Giant Spiders	Hiding in thick webbing; CL 2 to spot the webs.
15–18	Gelatinous Cube	Nearly invisible; requires a Wisdom (CL 3) check to notice.
19–22	3d6 Giant Rats	Led by a single "Rat King" (double HD/HP).
23–26	1d3 Gray Ooze	Blends perfectly with wet stone floors.
27–30	1d4 Trow Scouts	Horned hybrids wielding heavy mauls; naturally strong.
31–34	Fungi Forest	Non-combat; Violet Fungi or Shriekers mixed with edible moss.
35–38	2d4 Kobolds	Using small tunnels to fire shortbows with 3/4 cover.
39–42	1d6 Skeletons	Ancient miners still clutching rusted pickaxes.
43–46	Carrion Crawler	Scavenging near a previous battle site.
47–50	Dwarf Prospectors	Neutral party (1d6) looking for a lost silver vein.
51–54	2d4 Bugbears	Expert ambushers; Dexterity (CL 4) to avoid surprise.
55–58	1d4 Gargoyles	Perched on pillars or statues; appear as inanimate stone.
59–62	Shadow	Drains Strength; a terrifying threat for low-level parties.
63–66	Ogre Mercenary	Carrying a massive club; willing to negotiate for gold/food.
67–70	1d3 Hook Horrors	Using echo-location; party hears rhythmic clicking first.
71–74	Rust Monster	Specifically targeting the fighter's plate mail.
75–78	Wight	Resting in a forgotten stone sarcophagus.
79–82	2d6 Deep Gnomes	Svirfneblin merchants guarded by a clockwork construct.
83–86	Black Pudding	Corrosive; splitting into two if hit with slashing weapons.
87–90	Wraith	A malevolent spirit of a king who died in the dark.
91–94	Roper	Disguised as a stalagmite; pulls victims from 50ft away.
95–97	Mind Flayer	(Illithid) Accompanied by 1d4 Grimlock slaves.
98–99	Beholder	A young "Eye Tyrant" claiming this level as its domain.
00	The Master-Word	An ancient etched inscription. Reading it triggers a one-time class recharge.

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Environmental Hazards & Flavor

• Phosphorescent Moss: Provides dim "candlelight" illumination in a 10ft radius.

• Echoing Chambers: Sounds of combat travel twice as far here, potentially attracting a second roll on the table.

• Gas Pocket: A Constitution (CL 5) check is required or characters become fatigued from lack of oxygen.

CK Strategy: The Siege Engine in the Dark

In Castles & Crusades, remember that Strength and Dexterity checks are vital for navigating vertical terrain and narrow ledges. If the players are exploring an "Old School" style megadungeon, use the Charisma check to determine the initial reaction of intelligent creatures like the Ogre or Svirfneblin—not everything in the dark wants to fight immediately.

D100 Sword & Sorcery Underdark Encounters

This table focuses on the "weird fantasy" and "lost world" vibes common in Sword & Sorcery, moving away from standard high-fantasy tropes toward the atmospheric, the decayed, and the prehistoric.

d100	Encounter
01-03	The Glass Spire: A 40-foot needle of obsidian-like glass hums with a low frequency. Touching it grants a temporary vision of a prehistoric sun, but causes 1d6 psychic damage.
04-06	Fungal Herdsmen: 2d6 pale, eyeless humanoids herding giant, ambulatory puffball mushrooms. They are non-hostile unless their "livestock" is threatened.
07-09	Decaying War-Machine: A rusted, brass-bound brass behemoth from a forgotten era. It is immobile, but its interior serves as a dry, safe campsite—if you ignore the skeletal pilot.
10-12	1d4 Giant Albino Apes: Carnivorous and highly intelligent. They use simple tools and set crude traps in the narrow tunnels.
13-15	The Saffron Slime: A vibrant yellow carpet of ooze that smells like expensive spices. It is highly flammable and acidic.
16-18	Crystalline Scavengers: Small, beetle-like constructs made of quartz. They ignore organic matter but will attempt to "harvest" metal equipment from the party.
19-21	A Trow Exile: A solitary traveler with decorative horns and a heavy rucksack. They are wary but willing to trade information about the tunnels ahead for rare spirits or tobacco.
22-24	The Whispering Chasm: A narrow bridge over a bottomless pit. The wind rising from below sounds exactly like the voices of the party's deceased relatives.
25-27	Subterranean Jungle: A pocket of geothermal heat supporting a forest of giant ferns and bioluminescent vines. Watch out for giant dragonflies.
28-30	2d6 Morlock Raiders: Pale, cannibalistic degenerates wielding jagged flint knives. They prefer to strike from the ceiling.
31-33	The Fossilized God: The skull of a titan embedded in the cavern wall. Local tribes leave offerings of meat here; the meat disappears within an hour.
34-36	Magnetic Ore Vein: Metal armor and weapons become difficult to move. Movement speed is halved, and attack rolls are at a disadvantage while within 30 feet.
37-39	A Dying Sorcerer: An ancient man in tattered silks, clutching a glowing jade orb. He offers a "Master-Word" or secret in exchange for being carried to the surface to see the sky one last time.
40-42	Blind Cave Crocodile: A 15-foot prehistoric reptilian predator with heightened tremorsense. It remains perfectly still until it feels vibrations within 10 feet.
43-45	The Salt Nomads: A caravan of humans wrapped in grey rags, transporting blocks of luminous blue salt. They trade in "memory-dust."
46-48	Ghost-Lights: 1d8 floating spheres of cold fire. They lead travelers toward hazards like pit traps or gas vents.
49-51	Bat-Riders of the Deep: A scouting party of 1d4 warriors mounted on giant bats. They are looking for escaped slaves or intruders.
52-54	The Petrifying Mist: A slow-moving cloud of grey vapor. Anything caught inside must move quickly or find their skin beginning to harden into limestone.
55-57	Sun-Worshipping Ghouls: Undead who have carved a massive, crude sun into the cavern roof and spend their days "tanning" under bioluminescent lichen.
58-60	1d6 Giant Centipedes: Brightly colored (red and violet) indicating neurotoxic venom. Their chitin is valuable for making light armor.
61-63	The Singing Statues: A row of twelve marble statues that scream when a light source is brought near them, alerting every predator in the area.
64-66	Subterranean Lake: The water is perfectly still and black as ink. Something huge ripples the surface 100 yards out.
67-69	The Iron Hive: A colony of fist-sized insects that consume ore. They have begun eating the pitons or spikes the party has used to descend.
70-72	A Fallen Star: A metallic meteorite that crashed through the upper crust centuries ago. It is still warm to the touch and surrounded by mutated flora.
73-75	Serpent-Folk Emissary: An elegant, scaled humanoid in fine robes. They offer a safe passage through their territory... for a "minor" blood sacrifice.
76-78	The Echoing Plague: A fungal spore that causes the victim to compulsively repeat every sound they hear, eventually losing the ability to speak their own thoughts.
79-81	Obsidian Spiders: Spiders whose carapaces are sharp as razors. They don't use webs; they hide in the shadows and leap.
82-84	The Memory Well: A pool of silver liquid. Drinking from it restores a lost memory or a spent spell/ability, but ages the user 1d4 years.
85-87	2d4 Troglodyte Berserkers: Driven mad by a nearby "void-stone," these warriors fight with supernatural ferocity and ignore the first 10 damage they take.
88-90	The Clockwork Gate: A massive bronze door with no visible handle. It requires a specific musical note or a drop of royal blood to open.
91-93	A Swarm of Shadow-Moths: Their wings absorb all light. Torches and lanterns are extinguished within a 20-foot radius of the swarm.
94-96	The Lich-King’s Tax Collector: A high-level wraith demanding a "soul-tithe" (1 permanent HP or a valuable magic item) to pass through this sector.
97-98	Dimensional Bleed: For the next hour, the party can see into a parallel, prehistoric version of the cavern filled with lush ferns and dinosaurs.
99	The Great Worm: A Colossal purple worm is tunneling nearby. The cavern shakes violently; everyone must check to avoid falling debris.
100	The Vault of the Ancients: A hidden door leads to a pristine, white-marble laboratory containing one item of "Relic" tier technology or magic.

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Tips for Running:

• Encumbrance Matters: In the deep, every torch and ration is life. Encounters that destroy gear (like the Iron Hive or Crystalline Scavengers) are often more dangerous than those that just deal damage.

• The "Weird" Factor: If the party encounters a monster, describe its smell (ozone, rotting lilies, cold iron) and its bizarre movement before asking for initiative.

• Verticality: Don't forget that "underground" includes the ceiling. Use it for ambushes or environmental hazards.