A Cresthaven RPG Adventure for 4-6 Characters of 1st-3rd Level
Adventure Background
In the humble Village of Cresthaven, nestled amidst lush forests and rolling hills, a chilling rumor has been spreading like wildfire. Tales of giant spiders lurking in the woods have struck fear into the hearts of the villagers. Crops have gone missing, and livestock has vanished without a trace, leading some to believe that the eight-legged monstrosities are responsible.
These caves were once home to a goblin tribe, but they fled months ago when something far more sinister moved in. A Synapse Spider—a rare aberration with powerful psychic abilities—has claimed the deepest chamber as its lair. Using its mental influence, it has been coordinating the local giant spiders into an unnaturally effective hunting pack, making them far more dangerous than typical arachnids. The spiders didn’t just move in; they completely overran and eliminated the goblin clan that once called these caves home, leaving behind a chilling testament to their deadly efficiency.
Word of these sightings has reached the local Adventurer’s Guild, and it has drawn the attention of a group of aspiring heroes looking to make a name for themselves. The party, intrigued by the rumors, sets out1 to investigate the spider threat. That’s the last thing they remember before awakening trapped in the creature’s web.
Dungeon Master Tips
In Medias Res Start: The adventure begins with the party already captured, creating immediate tension and engagement. Don’t explain how they got there initially—let the mystery unfold as they explore.
Coordinated Spiders: Unlike normal giant spiders, these creatures are guided by the Synapse Spider’s alien intelligence. They use pack tactics, retreat strategically, and attempt to herd intruders toward their master’s lair in Area 8.
Psionic Atmosphere: Throughout the cave, describe subtle mental effects—whispers at the edge of hearing, feelings of being watched, and occasional flashes of alien thoughts. This builds toward the revelation of the Synapse Spider.
Lighting and Visibility: The dungeon is mostly Darkness. Light sources are crucial. Creatures without darkvision have the Blinded condition in darkness. Creatures with darkvision see normally in darkness. Describe shifting shadows and eerie illumination effects as the party uses light.
Webbed Obstacles: Use vivid sensory descriptions for the sticky webs. They cling to skin and clothes, make sounds when disturbed, and can be burned or cut through with creative solutions.
Time Pressure: The longer the party takes, the more coordinated the spider attacks become as the Synapse Spider learns their tactics and capabilities.
Goblin Remains: Emphasize the remnants of the goblin clan. This highlights the spiders’ destructive power and provides clues and grim atmosphere.
Terrain Effects: Apply the specified rules for Difficult, Unstable, Elevated, Narrow, and Steep terrain as described in each area.
Cave Encounters
1. Trapped!
You wake up entangled in sticky webs that cling to your skin like cold, wet rope. Your mouth tastes of copper and dust, and your head throbs with a dull ache. The air is thick and humid, reeking of dampness, decay, and something else—something sweetly rotten like overripe fruit mixed with old meat. Silken strands stretch across your vision, catching what little light filters down from somewhere far above. The webs pulse slightly with your heartbeat, as if alive and feeding on your warmth.
Faint skittering sounds echo through the oppressive darkness—not the random scrabbling of panicked insects, but something rhythmic and deliberate. Click-click-pause. Click-click-pause. The sounds seem to answer each other from different directions, like a conversation conducted in an alien language. Your skin crawls as you realize the truth: you’re not just trapped—you’re being studied by something far more intelligent than any simple spider.
GM Information: The party is restrained by giant spider webbing in the deepest part of the cave complex. To escape, they must succeed on a DC 15 Dexterity check or use a Strength attack against the web’s AC of 10. Failure means they remain restrained.
Light Level: This area is in Darkness. A faint, sickly phosphorescence emanates from some of the webs, providing Low Light in a very limited, immediate area around the characters, otherwise it is complete darkness.
Terrain: The thick webbing covering the floor makes this area Difficult terrain. Characters moving through it are affected by the Slow condition.
Failure Consequence: If a character fails their check to escape, there’s a 25% chance (roll a d4; on a 1, it happens) that a wandering giant spider hears the struggle and investigates. Since the character is restrained, they have disadvantage on any Dexterity save to avoid being webbed further, making them easy prey.
Atmosphere: Characters with high Intelligence may notice the skittering sounds have an almost rhythmic quality, like a heartbeat or breathing pattern—the first hint of the psychic coordination affecting the spiders.
2. Raised Dais
As your eyes slowly adjust to the gloom, shapes begin to emerge from the darkness. A raised platform of rough-hewn stone looms nearby, its surface worn smooth in some places and jagged in others. The stone is dark with age and stained with substances you’d rather not identify—rust-colored splotches that could be dried blood, and pale, crystalline deposits that catch the faint light like tiny stars.
Your gear lies scattered across the dais like offerings on an altar—your weapons gleaming dully, your pack’s contents spilled and sorted with unsettling precision. Coins catch the dim light, winking gold and silver against the dark stone. A glass vial filled with emerald liquid sits prominently displayed, and you can smell its sharp, medicinal scent even from here. But it’s the arrangement that disturbs you most—everything placed with deliberate care, as if by an intelligence that takes pride in its collection. Around the edges of the dais, you notice scattered, brittle fragments of what might be small bones, and bits of tattered, crudely woven cloth—relics of a former, less fortunate, inhabitant.
GM Information: The party’s equipment and treasure from previous victims are displayed on the dais. The treasures consist of 50 gold coins, a potion of healing, and a vial of spider venom. However, there’s a hidden tripwire in front of the dais that activates a concealed poison dart trap (1d4 poison damage, DC 13 Constitution save for half damage).
Light Level: This area is in Darkness. Any light source the party generates will illuminate the dais.
Terrain: The floor around the dais is covered in loose debris and discarded webbing, making it Difficult terrain. Characters moving through it are affected by the Slow condition.
Clue: Characters with a DC 12 Wisdom (Notice) check might notice that “one of the coins has been knocked slightly out of line… the only thing out of place in an otherwise obsessively precise arrangement.”
Details: This was once a goblin ceremonial platform. Careful examination reveals goblin skull fragments mixed with the webbing—evidence of the former inhabitants’ fate. Among the scattered debris are a few crudely made goblin trinkets (worth 1d4 gp each).
3. Blocked by Webs
The passage ahead is sealed by a wall of webbing so thick it looks like white wool stretched between the cave walls. The silken barrier rises from floor to ceiling, its surface glistening with moisture that drips steadily onto the stone below—plip, plip, plip. As you watch, the entire mass seems to breathe, expanding and contracting rhythmically as if it were the chest of some sleeping giant.
The air here carries a new scent—musky and organic, like the smell of a barn mixed with something sharper and more chemical. You can hear movement beyond the web wall: soft scratching sounds, the whisper of legs against stone, and occasionally a wet clicking noise that makes your teeth ache. The webbing itself seems to hum with barely audible vibrations, and you notice that touching any strand sends tremors throughout the entire barrier, as if the whole thing were one massive nerve ending. Embedded within the thick strands, you spot desiccated husks of smaller creatures, along with a few distinctly humanoid-shaped bundles, wrapped tightly and motionless.
GM Information: The passage is blocked by thick webbing requiring a successful DC 14 Strength check to force through. If the party attempts to cut through the web, they trigger a spider ambush: a giant spider descends from the ceiling and attacks with tactical precision.
Light Level: This area is in Darkness. Visibility is Obscured by the thick webs even with light sources, reducing normal visibility by half (e.g., a torch’s 15ft radius becomes 7.5ft effective clear vision, with disadvantage on Wisdom (Notice) checks beyond that).
Terrain: The entire passage is choked with dense webbing, making it Difficult terrain. Characters moving through it are affected by the Slow condition.
Tactical Note: This spider attempts to web the strongest-looking party member first, then retreats if badly wounded—showing unusual intelligence for its species.
Goblin Evidence: A successful DC 10 Wisdom (Notice) check on the wrapped bundles reveals them to be the mummified remains of goblins, drained of fluids and neatly stored. One of them clutches a rusted, crude goblin spear.
4. Trip Wire and Ambush
The narrow passage suddenly opens into a wider chamber, and the relief of expanded space is immediately replaced by a sense of wrongness. The air here is unnaturally still—so quiet you can hear your own heartbeat thundering in your ears. There’s an electric tension in the atmosphere, like the moments before a thunderstorm breaks, that makes your hair stand on end and your skin prickle with goosebumps.
Thin strands of webbing stretch across the chamber at various heights, creating an invisible maze of trip lines that glisten faintly in the dim light. Some are at ankle height, others at chest level, and a few hang from the ceiling like the strings of a puppet master. The web strands are so fine they’re nearly invisible until they catch the light just right, revealing the geometric precision of their placement. The smell here is different too—sharper, more acrid, like the air after lightning strikes. Something about this room feels like a trap waiting to spring. You notice fragments of crude goblin tools and weapons scattered on the floor, suggesting a hurried, desperate retreat.
GM Information: Trip webs are spread throughout this cavern. If players notice the webs (DC 15 Wisdom (Notice)), they can avoid the ambush. Otherwise, the tripwire activates an ambush of three smaller giant spiders that drop from the ceiling onto the party. The spiders attack with surprise, gaining advantage on their first attacks.
Light Level: This area is in Darkness. The tripwires are almost invisible even with light unless actively searched for.
Terrain: The uneven floor and sparse webs create Difficult terrain. Characters moving through it are affected by the Slow condition.
Coordination: The spiders demonstrate remarkable teamwork, focusing their attacks on isolated party members and using flanking maneuvers that seem far too sophisticated for their normal intelligence.
Goblin Remains: Scattered among the detritus are a few small, green-tinged bones and a couple of rusty goblin daggers, clearly abandoned in haste.
5. Nest
You step into a chamber that feels like walking into a nightmare. The ceiling arches high overhead, disappearing into shadows, but dominating the center of the space is a massive, grotesque egg sac the size of a wine barrel. The thing pulses and throbs with obscene life, its translucent walls revealing dozens of dark shapes writhing within. Veins of sickly yellow fluid run across its surface, and with each pulse, you can hear a wet, organic sound like a giant heart beating.
The sac hangs suspended by thick cables of webbing that stretch to anchor points all around the chamber, creating a web within a web. The air reeks of ammonia and something sweetly putrid—the smell of birth and death intermingled. Drops of viscous fluid fall steadily from the sac to splash on the stone below, where they hiss and bubble slightly. Around the perimeter, you can make out the outlines of smaller, shattered egg casings and piles of strange, dark refuse that might once have been goblin possessions, now mere debris in this monstrous nursery.
Guarding this abomination is a spider the size of a pony, her bloated abdomen glistening black in the dim light. Her eight eyes reflect what little illumination exists, creating tiny points of malevolent intelligence that track your every movement. She makes a sound—not quite a hiss, not quite a growl—that vibrates through your bones and makes your stomach turn. Her legs tap against the stone in a rhythm that matches the pulsing of the egg sac, as if she’s conducting some terrible symphony of reproduction.
GM Information: The egg sac contains valuable, gem-like spider eggs (worth 200 gp total) and a magic scroll with an insect-themed spell. The female spider is hostile and fights to the death, but if killed, the egg sac’s disturbance attracts two more giant spiders after 1d4 rounds.
Light Level: This chamber is in Darkness. The pulsing egg sac itself emits Low Light in a 10-foot radius around it, casting eerie, shifting shadows. Beyond this radius, it’s complete darkness.
Terrain: The floor around the egg sac is covered in sticky, discarded web strands and organic residue, making it Difficult terrain. Characters moving through it are affected by the Slow condition.
Psychic Influence: The female spider shows signs of the Synapse Spider’s mental control—she positions herself strategically and seems to anticipate the party’s movements.
Goblin Debris: Among the trash piles are broken goblin weapons, a few charred goblin totems, and small, crude musical instruments, hinting at the clan’s life before their demise.
6. Web Bridge
Before you stretches a bridge that defies nature—not built of stone or wood, but woven from countless strands of spider silk into a walkway that spans a yawning chasm. The bridge sways gently despite the perfectly still air, its movement hypnotic and unsettling. Each strand of the weaving catches the faint light differently, creating a shimmering, almost iridescent pathway that seems to writhe and shift as you watch.
The construction is remarkably sophisticated—far more complex than any normal spider could create. The webbing is braided and knotted with geometric precision, forming patterns that seem almost mathematical in their complexity. Support cables descend into the darkness below, their ends lost in the shadows. The bridge creaks softly as it moves, producing a sound like old rope under tension.
From the depths of the chasm comes the steady echo of dripping water—plip… plip… plip—each drop amplified by the enclosed space. The sound creates an eerie rhythm that seems to match the bridge’s gentle swaying. The air rising from below carries the scent of stagnant water and something else—something organic and unpleasant, like old bones left to bleach in the sun. If you peer into the depths, you might glimpse broken goblin scaffolding or the glint of discarded, broken pottery far below.
GM Information: The web bridge requires a DC 15 Dexterity check to cross safely. Failure results in a fall, taking 1d6 bludgeoning damage and attracting the attention of a lurking giant spider in the chasm below.
Light Level: This chasm is in Darkness. Any light source held by the party will illuminate the bridge and reveal limited portions of the chasm depending on its range. The chasm itself is so deep that only powerful light sources or magical light might reveal its true bottom.
Terrain: The web bridge itself is Unstable terrain. Anyone moving across it must make a DC 8 Dexterity save at the start of a turn (every 10 minutes, or once per round in combat on the bridge). On a failed save, a creature falls prone. The chasm floor below is effectively Difficult terrain due to debris and water.
Engineering: The bridge’s complex design hints at a directing intelligence far beyond that of normal spiders.
Goblin Remains: A successful DC 10 Wisdom (Notice) check reveals bits of crude goblin rope and discarded tools tangled in the webbing near the bridge’s anchors, suggesting the goblins may have attempted their own, less successful, crossing or escape.
7. Cave with Large Pillar
A massive stone column rises from the chamber floor like a giant’s finger pointing toward the darkness above. The pillar’s surface is covered in crude carvings—angular figures and jagged symbols that hurt your eyes to look at directly. The etchings seem to writhe and shift in the uncertain light, telling a story of panic and terror in primitive pictographs.
Dense webs shroud the pillar’s base like funeral shrouds, layer upon layer of silk that creates a gossamer maze around the stone foundation. The webbing here is different—older, yellowed with age, and it carries a musty scent like old parchment mixed with decay. As you watch, tiny motes of dust drift through the air, caught and illuminated by whatever faint light penetrates this deep into the cave.
The air in this chamber feels heavy and oppressive, pressing down on you like a physical weight. There’s an almost palpable sense of dread here, as if the very stones remember the terror that once filled this space. Your footsteps echo strangely, the sound seeming to linger longer than it should. From somewhere in the webbing comes the faintest whisper of movement—not quite a sound, more like a disturbance in the air that raises the hair on your back.
GM Information: The webs provide full cover to the cave’s resident giant spider as it waits to ambush the party. The pillar’s nooks and crannies hide treasure: a magical +1 dagger and a piece of enchanted +3 leather armor (for a total of +5 to AC when worn).
Light Level: This chamber is in Darkness. The dense webs at the pillar’s base create Obscured visibility within their area, even with light sources, giving disadvantage on Wisdom (Notice) checks or ranged attacks into or through them.
Terrain: The area around the base of the pillar is heavily webbed, making it Difficult terrain. Characters moving through it are affected by the Slow condition. The pillar itself offers opportunities for Elevated positions if a character can climb it (requiring a Climbing check). A creature at least 10 feet higher than its target on the pillar has Advantage on ranged attack rolls.
Goblin Carvings: The pictographs vividly tell a story of the goblin tribe’s flight from “the mind-eater” and “the spider-that-thinks.” They depict stick figures of goblins being ensnared by webs and dragged away by arachnids, or clutching their heads as unseen forces assault them. Characters who can read Goblin (or make a DC 15 Investigation check) learn that the goblins fled in terror from something that “spoke without words and saw without eyes.”
8. Lair of the Synapse Spider
You enter what was once a throne room, but it has been transformed into something from your worst nightmares. The chamber stretches out before you, its walls lined with the broken remnants of goblin civilization—overturned chairs, shattered pottery, and tattered banners that hang like moldy skin from the ceiling. Everything is draped in webbing that seems to pulse with its own malevolent life, glowing faintly with an inner phosphorescence that casts sickly green shadows on the walls. The chieftain’s crude throne is almost entirely obscured by thick, glowing webs, and a few small, mummified goblin bodies hang suspended like macabre decorations.
The air here is thick and oppressive, heavy with the stench of decay and something else—something sharp and metallic that burns your nostrils and makes your eyes water. You can taste it on your tongue, like copper pennies mixed with ozone. The very atmosphere seems to crackle with invisible energy, making your skin tingle and your teeth ache.
Where a chieftain’s throne once stood, a grotesque nightmare holds court. The creature is the size of a large dog, but that’s where any resemblance to normal life ends. Its body is translucent, like living glass, revealing the horrific anatomy within. Most disturbing of all is the hideously enlarged brain sac that bulges from its back, pulsing with veins of luminescent fluid and crackling with arcs of neural energy that dance across its legs like tiny lightning.
As it becomes aware of your presence, the creature’s multiple eyes—each one black and gleaming like polished obsidian—fix upon you with an intelligence that is utterly alien and completely malevolent. The air around it shimmers with psychic energy, and you feel something probing at the edges of your mind—cold, alien thoughts trying to worm their way into your consciousness. The sensation is nauseating, like having someone else’s fingers rifling through your memories.
GM Information: This chamber contains the Synapse Spider, the true threat behind the coordinated spider attacks. The room also contains the goblin chieftain’s treasures: a +1 magical sword, and a hidden secret compartment with a potion of invisibility and a scroll of protection from undead.
Some environmental effects or special abilities in combat occur at a specific point in the initiative order, often at Initiative count 20 or Initiative count 10. This means they happen at that precise moment in the round, before or after other creatures take their turns, creating dynamic and consistent battlefield conditions.
Light Level: The entire chamber is filled with Low Light due to the omnipresent phosphorescent webbing and the faint glow from the Synapse Spider itself. This provides enough light for creatures with darkvision to see normally, but others have disadvantage on Wisdom (Notice) checks that rely on sight.
Terrain: The floor is uneven and covered in layers of sticky webbing and goblin debris, making the entire area Difficult terrain. Characters moving through it are affected by the Slow condition. Additionally, the mummified goblin bodies and other suspended objects create areas of Obscured visibility, providing cover.
Combat Tactics: The Synapse Spider uses its Brain Web ability to disorient multiple party members, then employs Neural Slip to reposition while attacking with Psychic Lash and bite attacks. It targets the most intelligent party members first, recognizing them as the greatest threats.
Lair Effects: The psychically-charged webbing throughout the room creates the following effects:
Initiative count 20: Web strands animate to create difficult terrain in a 15-foot radius.
Initiative count 10: Psychic echoes force all creatures to make a DC 12 Wisdom save or be frightened until their next turn.
Initiative count 5: Psychic pressure causes a segment of webbing to rupture near a randomly chosen character, dropping them into a lower section (requires a DC 14 Dexterity save to avoid, or fall prone and take 1d4 bludgeoning damage).
Treasure: Beyond the chieftain’s gear, the Synapse Spider’s lair contains 1d4 psionic chitin shards (20 gp each, crafting components) and the wrapped remains of several mind-drained victims with their belongings (additional 100 gp worth of mixed coins and small valuables). Among these are identifiable goblin clan totems, pouches of crude goblin coins, and maybe a few rusted, but intact, goblin shortswords.
The Truth Revealed: Once the Synapse Spider is defeated, any remaining giant spiders in the complex lose their coordination and either flee deeper into the cave system or behave like normal, unintelligent arachnids.
9. Exit
The tunnel ahead begins to brighten, and you realize with a surge of desperate hope that you’re seeing actual daylight—not the sickly phosphorescence of the spider’s lair, but honest, clean sunlight filtering down from above. The air changes too, becoming fresher and cleaner with each step you take. The oppressive mental weight that has been pressing down on your consciousness like a physical burden suddenly lifts, leaving you feeling lighter and clearer than you have since this nightmare began.
As you emerge from the cave mouth, you’re greeted by the sight of blue sky and green forest canopy. Birds are singing—a sound so normal and beautiful after the alien horror below that it almost brings tears to your eyes. The sun warms your face, and a gentle breeze carries the scent of pine needles and wildflowers, washing away the lingering stench of decay and psychic corruption.
Fresh air fills your lungs, sweet and clean, and you can taste the difference—no more copper and ozone, no more the cloying sweetness of death. Behind you, the cave mouth yawns like a wound in the earth, but already the horror of what you experienced below is beginning to feel like a bad dream. The normal world has reclaimed you, and you are free.
GM Information: The exit leads out of the cave, and the party is free to leave. With the Synapse Spider destroyed, the spider threat to Cresthaven is ended. The party gains 400 XP for surviving the spider-infested cave, plus additional XP for defeating the Synapse Spider (450 XP) and any treasure obtained throughout their journey.
Scaling the Adventure
For Smaller/Lower Level Parties: Reduce the Synapse Spider’s hit points to 20 and limit its special abilities to once per encounter each.
For Larger/Higher Level Parties: Add 1-2 additional giant spiders to the final encounter or increase the Synapse Spider’s Potential Energy Pool to 24.
Conclusion
With the Synapse Spider eliminated, the coordinated spider threat is ended. The remaining giant spiders will disperse into the deeper wilderness, returning to their normal, solitary hunting patterns. Cresthaven is safe, but the adventure raises questions about what other aberrant creatures might be lurking in the deeper places of the world.
The psionic chitin shards and the goblin pictographs provide hooks for future adventures, hinting at a larger network of psychic threats that may have driven the Synapse Spider up from the depths in the first place.
This version should now be fully consistent with all your provided rules and preferences. Are there any other details you’d like to adjust or expand upon?
