Free D&D Dungeon: Deathtrap of Skarn

You know what D&D needs more of? Free dungeons. Here's one I spent 5 or so hours on, maybe more. I intend to test play it soon. It is intended for players level 3-5.

Plot Hook
The players are captured and placed in a dungeon designed as one large deathtrap by a Beholder (MM28) named Dungeon Master Skarn. He is obsessed with creating the greatest dungeon, which he calls Deathtrap. Deathtrap is his treasure. He lures adventurers and heroes and tricksters into his dungeon so he can put it to the test. Each victim gives him something to refine.

Dungeon Master Skarn's Deathtrap

      This dungeon is under constant watch and control by it's creator. He does not want his dungeoneers to get any rest. Any attempt the party makes at a short or long rest is immediately interrupted by the 1d4 Flying Sword and/or 1d4 Rug of Smothering (MM20) that decorate the walls and floors and/or Will-O'-Wisps (MM301) that are present everywhere and light the dungeon. Blink Dogs (MM318) and Phase Spiders (MM334) can also appear randomly if the party attempts to rest or spends too long in one spot.

      Ceilings are 20 feet high unless noted otherwise and the dungeon is bright in most rooms. Each square is 5 ft.

Room 1

The party begins in this round room. A well full of dark water is in the center. The walls show off a mural of what appears to be a beholder creating a dungeon in stages with numerous scenes of victims dying inside. When the party attempts to leave this room, they are ambushed by a Gibbering Mouther (MM157) hiding in the well.
     If the players want to examine the well after the fight for goodies, they can find 1d4 25 gp art objects at the bottom.

Room 2

In the wall of the opposite side of the room is a locked door 3 feet off the floor which prevents players from using brute force to open the door and requires them to use teamwork to access the lock and handle. In the center of the room is a pit 5 ft deep. A 30 ft stone column reaches from this pit to the ceiling. At the top, glowing lights show off a key. This key is for the locked door as well as the doors for the cages on the sides of the room. To retreive the key, players must climb the stone piller with a DC 15 strength or athletics check. Alternatively, the locks can be picked with a DC17.

      The cages are filled with corpses that rise as 1d4 skeletons (MM272) and 1d6 zombies (MM316) in each room and attack if the players enter. These zombies have shortswords and are dressed in padded armor, giving them a total of 9 AC instead of 8. Each cage also contains a mimic (MM220) disguised as a treasure box that awakens and attacks only when the players attempt to open it.

Room 3

This long hallway has a 20 ft by 40 ft pit, 10 ft deep. This gap in the hallway is only spanned by 20 ft tall wood posts. Each post is wide enough for someone to balance one foot on. The players can only cross this pit by making a 15 DEX or acrobatics check. To proceed, the players have to use team work to push open one large, heavy door on the other side.

Room 4

This room is a split level. The upper section is 5 ft up, but 5 ft castle-like battlements wrap the perimeter and provide half cover or more for creatures on the upper level. This room is populated with zombie versions of non-player characters from appendix B (MM342) of the monster manual which include 1 Spy and 1 Cult Fanatic using ranged attacks from the safety of the upper level; One stair well is guarded by 1 Bandit Captain and the other stair well is guarded by 1 Berserker. The Berserker and Bandit Captain will not pursue players past the stairs. They each have the Undead Fortitude ability, refer to zombies in MM316. Pick one of these creatures to have a key that unlocks the double door to the next room.

Room 5

This room has several magic items as display items like pieces in a museum and are all cursed.  If the players wield or wear any of the display treasures, roll from the Tricks table on page 298 of the DMG.

      The room to east is a 20 ft deep, deadly spiked pit. Players can safely climb down with a rope. Players who jump down make a DC16 DEX or acrobatics check to avoid taking 4d10 piercing damage. The floor is covered with coins and gems, and there are even some other treasures present.

     For treasure available in this room and for treasure and coins available in the spike pit room, see the Treasure Hoard: Challenge 0-4 table of the DMG. This is where Skarn dumps his treasure.

Room 6

The hallway preceding this room is only 10 ft high, is dimly lit, and has a trip wire trap. The lead party member must make a 15 WIS or perception check or the trip a trip wire. All party members standing in this hallway must make a 15 DEX Save or take 2d6 piercing damage from metal skewers that shoot from nearly invisible holes in the floor.

      There are 2 pressure plates hidden in the floor in this dark room. Characters weighing 50 lbs or more must make a 15 WIS check or they will step on one of these plates. If the character does not have a light source or darkvision, they automatically fail this perception check. As a result, gates engage, blocking both ends of the hallway. These gates are locked and can be picked, but the key is worn in plain view by the creature at the far end of this room.

      However, the creature in this room is a displacer beast (MM81) with a passive perception of 11 and darkvision. It is unchained by the players stepping on the pressure plate and it attacks the players immediately. If the party manages to avoid triggering the pressure plates, the displacer beast, which move just enough that it can reach anywhere in the room with its tentacles, will attack if it is approached or if the secret exit is found.  Players trapped behind the gate can use ranged attacks through the gaps in the gate at disadvantage.

      A secret exit is hidden in the wall opposite from the entrance to this room. Players need only pull a lever disguised as a candle. This ceiling of this hallway is only 10ft high and is dimly lit after it turns.

Room 7

At the end of the hall is a narrow archway. Passed that is the chimera's lair (MM39) with a 40 ft high ceiling. In the middle of the room is a 20 ft diameter, 10 ft high dome. Players go no further without successfully sneaking past this creature with a successful DC 19 Stealth check, defeating it, or outrunning it. If one party member fails the stealth check, the the Chimera will immediately see all party members not hidden by the stone columns or out of sight behind the archway. Due to its size, the chimera is restricted to this room.

Room 8

Another narrow archway on the other side of the chimera's lair leads to a long corridor with 30 ft arched ceilings. This room is lined on all sides by statues of various creatures. As soon as the party reaches the midway point of this room, 1d4 of the statues animate as gargoyles (MM140) and attack; At least one gargoyle is behind the party.

Room 9

Dungeon Master Skarn's Lair is a split level room. Each level is 10 ft higher than the previous level. Skarn is a beholder and he's very satisfied with the players who make it this far. Skarn has a loud voice and speaks like someone who is proud and boisterous. The players are given the choice of becoming loyal servants of Skarn in exchange for their lives. If they all refuse, he will attack the party and place their corpses in the cages in room 2 if he doesn't turn them into stone and decorate the dungeon with them.

      If the party is split, Skarn will order the players who agree to become his servants to kill the other players.

      If the entire party agrees to serve Skarn, he will order each of them to prove their loyalty by sacrificing something valuable to his collection. They may choose to offer a magical item that is not a magic scroll (cantrip) or a potion of healing which the players brought with them. He will accept a wizards spell book. Skarn will also order them to return any treasure they collected in his dungeon.

      Now that the players have agreed to become servants of Skarn, they are given a curse. This curse ensure that they do not betray him once they've left his sight and his reach. They are set loose on the world. They must find additions for his dungeon, such as monsters or magic items, or lure adventurers, warriors, wizards, rogues, and et cetera to their dooms here.

      It is not possible for low level players to defeat Skarn, but the exit is behind him. If the players disappoint Skarn, one possible punishment Skarn threatens PCs with is to be made an undead guard and defend the dungeon from the next round of dungeoneers who enter.