This scenario is part of a larger campaign, but could certainly be used as a one off adventure or folded into an existing story. It was concepted and designed for D&D 5e, but could easily be modified for other game systems.
The cave was once an old coal mine that bore little fruit over two hundred years ago that had since been abandoned. The cave was discovered and became occupied by a group of Vampires a little over twenty years ago. This gang is lead by Mossimo, a veteran servant of the great Vampire King Vlad Tepes.
Mossimo’s goal was to grow his gang and gather intel in the region. Establishing a stable food supply near the hideout proved to be problematic. His current plan is to slowly wear down and overrun the local frontier settlement of Estermarsh. The town seems hell bent on killing all things not human. The town’s Mayor, Folke Avet, has established a deep set xenophobia among his flock. His racist roots have grown so deep into his sense of self that no line of logic can persuade him otherwise.
A pact once existed between the Vampires and the Humans of Estermarsh: They provide regular offerings of pigs blood cut with human blood and the town would remain protected from the wild beasts of the frontier. Once Folke was elected, he moved quick to destroy the pact by framing the vampires as monsters. Since then, random attacks against the Vampires became common so retaliation was in order. Every few months, the Vampires abduct a citizen of Estermarsh to use as a source of nourishment.
Area I (Cave Exterior):
The cave entrance looks as if it is not natural. An investigation check (DC 5) reveals that it looks like it was a mine, but must be a few hundred years old. The ground is worn from heavy use. The entrance is clean and free of debris, very open. It is definitely occupied. A faint flicker of lamp light can be seen inside, just barely.
Area II (Cave Entryway):
Collapsing roof trap – uses a tripwire 3 in. off the ground halfway into the entrance between two support beams. DC to spot is a 10 (WIS), DC 15 DEX check using thieves tools to disable. can be attempted at a disadvantage without thieves tools.
IF beams are inspected, it can easily be determined they are just wedged in place. Anyone who inspects the ceiling can tell it is in danger of collapse.
Any creature under the area of ceiling that collapses, must succeed on a DC 15 DEX saving throw taking 22 (4d10) bludgeoning damage on a failed roll or half damage on a successful save. once triggered, the floor under the trap becomes rough terrain.
If the trap is triggered, the vampires in area 2 can hear the ruckus..
Area III (Entry Chamber):
[Lowest HP Vamp Spawn, 30 HP each (MM pg. 298)] One Vampire will be up on a ledge (bottle neck) while another is down below near the entrance concealed in a coffin. The vampire in the coffin will emerge if the party makes considerable noise. It will lay in wait if it is altered in anyway, then emerge at the most opportune moment.
MORAL QUANDARY: The Vampire will first shout out to ask who is entering the cave. If the party engages in battle, the vampires will make a few pleas for the fighting to stop. If dialog opens up, they will be more than willing to explain how they need the villagers to survive (they can’t help that they are vampires after all, can be framed into a “do you feel bad for the animals you eat to stay alive” type argument.).
Area IV (Holding Cell):
Two humans are in the holding cell. One is recently dead, the other is weak and only a few days from death. The survivor can inform the party about the abduction and how the vampires use them as a food source. The survivor is a traveler from Byfox named Monder (Male Human Fur Trader, LG. Str 12, Dex 11, Con 11, Int 13, Wis 5, Cha 9. Monder has thick blonde hair and soft hazel eyes, and a thin nose. He wears modest garments and several small tools hang from his belt. Monder compulsively scratches an old scar.) He was hunting around the Dreadmoore Forest when he was abducted. The deceased victim is a middle aged male name Helmund, and was a citizen of Estermarsh.
Area V (Winding Tunnel):
Several groups of bats are hanging from the ceilings in this area (Swarm of Bats MM pg. 337). The ceilings are about 15 feet high. The tunnel is not lit and is pitch black. A DC15 perception check will allow the party to notice the bats, or if someone decides to deliberately check the ceiling. If any loud noises are made, it will activate the bats which will alert the Vampire in Area VII. The bats will attack the party for 1d4 rounds and will mostly disperse into the depths of the cave to escape the party.
Area VI (Cave Pond):
The opening into the Cave Pond from the Winding Tunnel is very narrow and short, the opening is 2 feet off the cave floor. A Dwarf may be able to crawl through on a successful DC12 DEX save. If failed, the player gets stuck and will need to be dislodged by the other players (DC5 STR save to remove, DC 10 DEX save from stuck player and pullers to make sure they don’t tumble and make too much sound). If the players make too much sound, the Vampire in Area VII is alerted. A creature smaller than a Dwarf can easily crawl through the opening.
The water can be silently traversed on a successful DC 5 stealth check. The pond is only 1.5 feet deep. The water is crystal clear, if the player bothers to look down at all or investigate the water, they can easily see the tunnel that leads to Area X. If the player makes noise in the pond, the Vampire will come and investigate immediately.
Area VII (Living Chamber):
[Medium HP Vamp (MM pg. 297), 40 HP] One Vampire will be watching down a long corridor and will cast fire bolt (cantrip, 1d10 fire damage, range 120 ft) at the party if they act hostile. (This vampire has a giant pet bat (MM pg. 323) at it’s side)
Area VIII (Hallway):
This hallway transitions from the natural formation of the cave to a precisely crafted and finished hallway. The walls are smooth and seamless, perfectly square from what you can see. The hallway ends in a heavy wooden door that fits perfectly snug into the wall. The door is unlocked.
Area IX (Inner Sanctum):
[Full HP Vamp (MM pg. 297)] Vampire Boss. Free for all melee in the main chamber.
MORAL QUANDARY: The Vampire boss if engaged verbally or if he knows the players are coming, will be impressed that they made it to his chamber and will offer them immortality as vampires in exchange for being in the service of Lord Tepes. If they refuse, combat begins.
The crafted hallway continues on and takes a 90 degree turn into a room that is concealed by a large red curtain, it is thick and heavy. If the players have been quiet while opening the door and sneaking in, the Vampire in the final room will be unaware and will be focused on a dark ritual that he is performing (he is communicating with Lord Tepes using a magic orb, if he is undisturbed then the players can listen in). Laid out on the table before him is a large blue tome (Tome of Town Portal) and one half of the Tempest Cave Seal.
Area X (Flooded Chamber):
This large flooded chamber is pitch black. At the bottom of the 10 foot deep pool, the players can find the following scattered on the chamber floor:
2400 cp, 1200 sp, 90 gp, Banded agate (10 gp), Blue quartz (10 gp), Lapis lazuli (10 gp), Moss agate (10 gp), 4 x Tiger eye (10 gp), Turquoise (10 gp), Potion of Fire Breath, Potion of Water Breathing, Helm of Telepathy (must be attuned to it)