35. Reliquary
The ghostly chant emanating from area 38 fills this room. Characters can discern a dozen or so voices saying, over and over, "He is the Void. He is the Stars."

The cult amassed several "relics" that it used in its rituals. These worthless items are stored in thirteen niches along the walls:

- A small, mummified, yellow hand with sharp claws (a goblin's hand) on a loop of rope
- A knife carved from a human bone
- A dagger with a rat's skull set into the pommel
- An 8-inch-diameter varnished orb made from a nothic's eye
- An aspergillum (as-per-Jill-uhm) carved from bone
- A folded cloak made from stitched ghoul skin
- A desiccated frog lashed to a stick (could be mistaken for a wand of polymorph)
- A bag full of bat guano
- A hag's severed finger
- A 6-inch-tall wooden figurine of a mummy, its arms crossed over its chest
- An iron pendant adorned with a devil's face
- The shrunken, shriveled head of a halfling
- A small wooden coffer containing a werewolf's withered tongue

The southernmost tunnel slopes down at a 20-degree angle into murky water and ends at a rusty magnetic door (area 37).

36. Observation Room
The cult used this room to observe the experimental rituals they underwent in area 38.  All the computers are not functioning, and analysis of their components shows that even if they could be repaired, any useful data would be lost.  A DC 15 Tinker Tools check followed by a DC 15 hacking tools check allows one to open the magnetic door leading to area 38.

A secret hatch can be found under one of the tables that leads to the ritual room.

A skeleton with a white lab coat can be found leaned against one of the tables, a gold ring (worth 25 gp) wrapped around one of its fingers.

37. Magnetic Door
This tunnel is blocked by a rusty magnetic door that can be forcibly pulled open with a successful DC 20 Strength (Athletics) check. Otherwise, door can be opened by someone in the Observation Room who has repaired the computer. The floor around the portcullis is submerged under 2 feet of green slime.

38. Ritual Room
The cult used to perform rituals in this sunken room. The chanting heard throughout the labs originates here, yet when the characters arrive, the dungeon falls silent as the chanting mysteriously stops.

The chanting stops as you peer into this forty-foot-square room. The smooth metal walls provide excellent acoustics. 12 feet in the air is the Observation Deck, with its dirty glass being the only thing separating the two rooms. Green sludge covers most of the floor. Stairs lead up to dry metal walkways that hug the walls. In the middle of the room, more stairs rise to form an square dais that also rises above the muck. What can only be described as a medical device created for torture dangles from the ceiling directly above a surgery table mounted on the dais. The altar is carved with hideous depictions of grasping ghouls and is stained with dry blood.

The sludge is 2 feet deep. The ledges and central dais are 5 feet high (3 feet higher than the water's surface), and the chamber's ceiling is 18 feet high (13 feet above the dais and ledges). The cult would sacrifice prisoners on the dais, letting their blood drip into the sludge below.

A hidden door in the south wall leads to a small chamber. The creature within is a shambling mound, the the cultists dubbed Lorghoth the Decayer.  It is asleep but awakens when a creature fails the check to open the magnetic door from the Observation Deck (see area 36) or if the characters summon the cultists but refuse to complete their ritual (see "One Must Die!" below). A character standing next to the door can discern its with a successful DC 15 Perception check.

"One Must Die!"

If any character reaches the top of the dais read:

The chanting rises once more as thirteen dark apparitions appear on the ledges overlooking the room. Each one resembles a black-robed figure holding a torch, but the torch's fire is black and seems to draw light into it. Where you'd expect to see faces are voids.

"One must die!" they chant, over and over. "One must die! One must die!"

The apparitions are harmless figments that can't be damaged, turned, or dispelled.

Characters on the dais when the cultists appear must sacrifice a creature on the table or face the cult's wrath; characters can ascertain what must be done with a successful DC 11 Intelligence (Religion) or Wisdom (Insight) check. To count as a sacrifice, a creature must die on the table. The apparitions don't care what kind of creature is sacrificed, and they aren't fooled by illusions.

If the characters make the sacrifice, the cultists fade away, but their tireless chant of "He is the Void. He is the Stars," echoes again in the dungeon. Strahd is aware of the sacrifice, and Death Labs now does nothing to hinder the characters (see "Endings" below).

If the characters leave the dais without making the sacrifice, the cultists' chant changes: "Lorghoth the Decayer, we awaken thee!" This chant rouses the shambling mound and prompts it to attack. It pursues prey beyond the room but won't leave the dungeon. It can move through tunnels without squeezing and completely fills its space. At the start of the shambling mound's first turn, the chant changes again: "The end comes! Death, be praised!" If the shambling mound dies, the chanting stops and the apparitions vanish forever.

Endings

The Cult Is Appeased

Death Labs harbors no ill will toward a party willing to sacrifice a life to appease the cult. Once the sacrifice is made, the characters are free to go. Upon emerging from the labs, the characters advance to 3rd level.

The Cult Is Denied

If the characters deny the cult its sacrifice and either destroy the shambling mound or escape from it, Death House attacks them as they try to leave. When they return upstairs, they must roll initiative as they discover several architectural changes:

- All the windows are sealed up; metal reinforced windows and the outer walls are impervious to the party's weapon attacks and damage-dealing spells.

- All the doors are gone, replaced by moving laser beams. A character must succeed on a DC 15 Dexterity (Acrobatics) check to pass through a laser-trapped doorway unscathed. A character who spends 1 minute studying the lasers in a particular doorway can try to take advantage of a momentary gap in their repeating movements and make a DC 15 Intelligence check instead. Failing either check, a character takes 2d10 fire damage but manages to pass through the doorway. Any creature pushed through a doorway must succeed on a DC 15 Dexterity saving throw or take the damage. The lasers can't be disarmed.

- Every room with a metal grate is filled with poisonous gas.  The gas slowly spreads, filling the entire house within 1 minute. Affected rooms are lightly obscured, and any creature that starts its turn in the gas must succeed on a DC 10 Constitution saving throw or take 1d6 poison damage.

- The interior walls become rusted and brittle. Each 5-foot-section has AC 5 and 5 hit points, and can also be destroyed with a successful DC 10 Strength (Athletics) check. Each 5-foot section of wall that's destroyed causes a swarm of beetles to pour out and attack. The swarm won't leave the station.

Keep track of initiative as the characters make their way through the house. Once they escape, they advance to 3rd level, and the house does no more to harm them.