What would you do if you woke up at a picnic, with no memory of how you got there?
This is a stand-alone adventure intended for you to work into your campaign if you are experiencing writer's block, or if your players go somewhere unexpected. Please change names and other details around to best suit your world. This adventure works best if the party has been dealing with a powerful magical foe who could have knowledge of this arcane prison.
This adventure is designed for three or more level 8 characters. Creatures from the Monster Manual (abbreviated MM) are used. Many of these creatures are listed in a range of numbers. Use the largest number for groups of five or more players, the smallest number for groups of three players, and the average for groups of four.
A Mysterious Picnic
This adventure begins as the player characters awaken sitting on red gingham blanket spread with food and drink. Surrounding them is an idyllic valley smelling of fresh-cut grass. They have no memory of how they got here. The food and drink appear every day at dawn, as if created by the spell create food and water.
There are a few copses of trees, but no animal life to be found at all. Towards the edge of the valley is a river flowing clockwise around the entire perimeter. It has no tributaries and seems to run perpetually across level ground. A marid (MM pg. 146) lurks in the river and rises up to prevent any who approach it from crossing with deadly force.
This whole area is actually a magically-induced shared hallucination of sorts. The entire valley behaves as if under an antimagic field, except for the food, the river, and its marid guardian. Should a character cross the river, their body falls down dead and they awaken back in “reality” in area 6 at the start of their next turn. If a character is reduced to 0 hit points, they also immediately die and wake up in area 6. However, in this case, they take 2d10 psychic damage, or half if they succeed on a DC 13 Charisma saving throw.
The Prison
This entire structure is constructed out of a smooth, gray, concrete-like material. This material is about 2 inches thick in most places, underneath which is rock and soil- indicating that the entire area is subterranean. Doors are all made of copper and slide open.
This was once a prison used by a long-dead civilization. Its occupants have their minds transported to the picnic area, while their bodies remain in the physical realm.
Random Encounters
Two optional “random encounters” have been included for the prison area. You may ignore these, throw one in should the game start to slow too much, or check with a d20 roll at the specified intervals.
Frequency Chance of Encounter
Every 10 minutes 1-2
During a short rest 1-10
During a long rest 1-20
On an EVEN result...
An invisible stalker (MM pg. 192) sweeps through the prison, accompanied by 0-2 invisible will-o’-wisps (MM pg. 301). They have been tasked with eternally guarding the prison and escorting anyone they find wandering around back into their cells. The creatures attack any who resist.
On an ODD result...
A mind flayer (MM pg. 221) named Qerbudem is exploring the prison. It is interested in the arcane technology that powers this place, and has helped itself to a snack in area 7. Qerbudem is surprisingly non-confrontational, but has no reason to aid the party. If Qerbudem feels its life is threatened, it uses plane shift to escape (which is how it got in here in the first place).
1. Control Center
This room is much larger than most of the prison, with four pillars supporting the ceiling above. Unlike most of the smooth walls found in the rest of this area, the wall opposite the entrance is studded with several gems, some of which glow with a dull light (see below). In the middle of the room is a circle covered in sigils. Succeeding on a DC 10 Intelligence (Arcana) check identifies this as some form of teleportation circle.
If anyone touches any of the gems, they are greeted by a disembodied voice speaking in Primordial. The voice belongs to a magical intelligence that runs this prison facility. Its mind has degraded over centuries, and it doesn't really know what it's doing any more. Occasionally it uses its powers to teleport a group of creatures to its realm. It attempts to answer questions, but most of its answers are gibberish, if not outright lies.
The 13 gems are easily pried out from the wall and are worth about gp each. As soon as one is removed, the light fades and the voice does not come back. This shuts down the prison, freeing the duergar in areas 9 and 10, but all of the autonomous creatures remain active.
2. Corridor
This angular hallway gently rises up at least 40 feet clockwise from area 1 to area 11.
3. Storage
The walls of this room is lined with niches in which are stored the possessions of the party, the duergar, and several other miscellaneous pieces of adventuring gear. Notable among these is a magical suit of studded leather armor. The studs are in the shape of golden suns and the armor grants resistance to radiant damage. There is also a total of 700 cp, 6,000 sp, 2,000 gp, and 60 pp spread out among several different coin purses.
This room is attended to by 3-5 copper automatons (using the animated armor statistics- MM pg. 20). As with the invisible stalker, they will attempt to force anyone they find back into cells. Will-o'-wisp servants will repair any destroyed automatons over the course of 1d6+1 days.
4. Collapsed Cell
This room has collapsed and rubble has fallen against the door, making them difficult to open. Not only that, but the doors have become electrified. Anyone who succeeds on a DC 15 Wisdom (Perception) check notices a hum coming from the doors. Any creature who touches the doors directly takes 2d10 lightning damage.
5. Smashed Cell
This cell is similar to area 6, except that the beds have been smashed apart and the wires pulled down and scattered about. It is otherwise empty.
6. Cell
When any of the player characters awaken from the picnic realm, they find themselves strapped down to a small cot with copper electrodes running from their head to the pillar in the center of the room. Escaping the restraints requires a successful DC 10 Strength or Dexterity (Athletics or Acrobatics) check. Removing electrodes from one of their companions removes them from the picnic realm as if they had crossed the river.
Make it clear to the players that their weapons, armor, and equipment have all been removed (see area 3).
7. Qerbudem's Leftovers
This cell is similar to area 6, with three recently-deceased gnomes strapped down to the cots. Casual investigation shows that each one has had their brains sucked out through a hole in the skull (see random encounters).
8. False Prisoners
A succubus (MM pg. 285) named Belmaz and its 2-4 doppelganger (MM pg. 82) servants are lying in wait here. They use read thoughts to choose forms they believe will be appealing to the party and then pretend to be trapped in the picnic realm.
Belmaz uses this prison as a hunting ground for vulnerable souls. It knows the password to allow passage past the copper golem: sevit revi. It does not give this information up easily.
9. Duergar Prisoners
Five members of a duergar (MM pg. 122) war party lie here unarmed, imprisoned in the picnic realm. Their leader, a female named Arniss Bloodstone, speaks for the group and makes their decisions. She works with the party if it appears to be in her best interests, but betrays them as soon as possible. Arniss claims that the treasure in area 3 originally belonged to their group. If a battle looks difficult (such as in area 11), she and her companions will turn invisible and abandon the player characters.
10. More Duergar
1-5 more duergar warriors (see area 9).
11. Exit
This room is similar in size and shape to area 1, but instead of crystals, the far wall is set with a double door that leads outside into the wilderness. This door is guarded by a large automaton made of copper (using the statistics of a flesh golem MM pg. 169) and 3-5 will-o'-wisps (MM pg. 301). The automaton does not allow anyone to pass in or out unless they utter its password, sevit revi. In combat, the will-o'-wisps will prioritize healing damage done to the automaton with their shock attacks. Will-o'-wisp servants will repair any destroyed automatons over the course of 1d6+1 days.
Continuing From Here
The location of the prison might be hundreds of miles from where the party last was, or very close. Their imprisonment may have been an intentionally malicious act, or just a random whim of the magical intelligence that runs the prison. This is up to you to decide and the players to stress over figuring out.