A level 3 dungeon for 5e

I have recently realized that I have never actually played any of these high-crunch tactical grid combat modern heroic RPGs as intended. Reading about encounter balance and all that actually got me interested in a more formulaic, structured game as an experiment. So I joined a 5e "westmarch" server ran by a friend and started running.

Notes about the balance of this one: The characters start at level 3 and there are three of them. There are piles of magic items and gold as despite starting at third, the party has no extra equipment. The group is expected to be able to finish all 3rd level content in one adventuring day, take a long rest, then return to finish up the adventure which should take them to 5th level.

The Hook:

An entrance to a dungeon has been unearthed recently, a few days of walking from the nearest settlement. Another, weaker party has recently ventured in, but have never returned. 

The Map:

 

  

The Key:

1. Entrance room. Stairs lead up, outside of the dungeon. Party will notice the dungeon is in bad repair, moist and overgrown with moss, dungeon grass and other vegetation. Table in the south-east corner is overflowing with rotting food. Hidden amongst the decay is key number 1.
2. There is a gelatinous cube in the western alcove. Within the cube there floats a Shield +1 (emblazoned with an eye, whole shield transparent from the wielders perspective) and a Belt of Gender Bending (braided blue with a silver buckle). To the east there is what seems like an archway to nowhere. Searching that spot will reveal a secret door.
3. On the eastern wall there is chalk writing "Beware of the gelatinous cube to the south". North-west corner is overgrown with a huge bush. Investigation will reveal a heavily overgrown and dangerous crawlspace that only parties with a ranger may travel through. In another corner there is a discarded backpack containing 300gp, a coil of rope, a torch, a Healing Potion, a holy symbol and a whistle.
4. This room is occupied by a small group of a false ogre and three orcs. The false ogre is wearing Gauntlets of Ogre Strength and will revert back into a normal orc should they be removed. A few benches and weights are placed in the room which they use for excercise. They have a Potion of Climbing, an Immovable Rod and 600gp hidden in a locked chest. The ogre has the key.
5. Six identical statues stand in two rows depicting armored warriors. A Magic Mouth announces to "Speak the command word!". The command word is "Sheakorak". Upon activation the statues will announce that each will perform one service. If asked to fight treat them as Animated Armor. Statue 2 will actually behave randomly when its time to act, and statue 6, which radiates evil if detected for, will betray and backstab the party given the opening.
6. A place of horrible slaughter - the floor is covered with the blood and guts of 4 adventurers torn to bits by claws and fangs. They have already been looted, but one of them is laying on a plaque which fell to the floor. The word "Sheokorak" is inscribed on it.
7. A wandering Dungeon Merchant has set up shop in this room. He is a cloak covered figure, with two large glowing eyes and smile under the hood being the only distinct features. Detects lies, never lies himself, cannot be haggled with but might accept exchanges, never engages in combat and immediately teleports away with his inventory should violence or thievery be attempted. All of these qualities are immediately apparent to anyone who sees him. His wares are displayed on the table next to him in the south-west corner of the room:
   Key number 2 (merchant will gladly disclose that the keys are used to open the double door to room 18) for 100gp
   Boots of Striding and Springing for 500gp
   Half-empty Keoghtoms Ointment (2 uses) for 200gp
   Golden Acorn (immediately grows into a great oak when thrown into soil) for 200gp.
   The left door north is locked (DC18), the key held by the skeleton sniper.
8. A powerful Skeleton Sniper (as skeleton, armed with longbow, 2 attacks, 24 dex, 17 AC) equipped with Bracers of Archery takes cover here behind a wooden barricade. He will fire upon anyone crossing the chalk line (dotted line down south) and try to run if they approach from another direction. Firing at him from south will yield no effects as long as the barricade stands. He is aware of the secret door to the west.
9. A statue of a thinking man stands by the west wall of this room. His head is backwards, facing the ceiling. Anyone touching this magical object will have their highest and lowest ability score swap values. Obviously, this only works once per person. This effect can be undone by Greater Restoration or winning a deadly fight while pretending to be a different class, say a heavy armor fighter could try a rogue-like approach, or a wizard could take up a greataxe and mimick a barbarian. Both methods are apparent to the one cursed.
10. This room belongs to a group of six goblins. Their arrows are poisoned, dealing extra d10 poison damage on a hit should a DC13 constitution save be failed. This poison disappears after four hours without dipping it in goblin piss. Their sleeping places, packs and piss pots are by the northern wall. 3000sp can be discovered if those are searched. The door west is barred. Generally, the goblins are positioned by the southern exit, ready to ambush anyone going down the corridor where they have discovered a pit trap. (Passive perception of 16 or better to notice seams and slight sagging of the floor. Opens when heavy weight is placed on it, such as two adventurers, dropping them down 10' and onto goblin-placed punji sticks dealing 2d10 damage unless a DC14 dexterity saving throw is passed. A 1-foot ledge around the pit is safe to travel.)
11. The stairs from south go down 15' into this 5' deep pool of opaque shit-water. An Otyugh inhabits the pool, and will telepathically prompt anyone standing on the edge of the balcony above to jump in. It can reach people standing on the balcony with its tentacles, but not if they are in the corridor behind it. If no targets present themself, the otyugh hides under the balcony until they go away. It is too big to pursue through the door on top of the stairs.
    Given a search, a clogged grate will be revealed on the western wall. At the end of the pipe behind it there is a room with a slide that goes god knows where and a chest of treasure containing 800gp, a Robe of Powerlessness (brown with silver trim), a Healing Potion, a Potion of Hill Giant Strength and a Club +1 (a good looking stick)
12. This room is filled with a tranquil aura and faint blue light emanating from a magical fountain by the southern wall. The fountain is a statue of a woman in robes pouring from a flask, and the water in the pool under it is perfectly clean. Drinking from it restores 2d8 HP, but only works once per day for any given person. The door west is sealed with holy writs and wax, standard way to ward off evil forces. The sealing may be trivially removed given a few minutes.
13. A dank malignant aura fills this room. At the far end there is a withered corpse of an armored man. He has the following items in his pack: Scroll of Cure Wounds, a rip-activated Scroll of True Strike and 700gp. He is wearing Adamantine Plate Armor however the item is ruined now and must be repaired for 1500gp to be usable.There are several alcoves along the walls here filled with piles of bones, yielding a Scroll of Light and 250gp if searched. Disturbing any feature of this room will cause the corpse to emit an ear-piercing shriek, awakening 3 Skeletons and 4 Shadows.
14. Two one-way doors lead to this room, seemingly locking the party in. There is key number 3 on the floor here. A plaque on the eastern wall reads "You are stuck here forever!". The simplest way to escape this room is via the secret door to the north. Random encounters do not appear here.
15. Upon entering this room by the north-western door the wimpy orc hiding behind a wooden wall will pull the trigger on a triple crossbow trap which performs three attacks at +8 to hit against the opener, each dealing d12 damage on a hit. He is likely to surrender if whatever went through isn't killed by that. He hid 200gp in his little fort. A pile of rubble in the south-east corner conceals a secret door.
16. This is the surveilance room of Mage Delimal, the current lord of this dungeon. It appears to have been hurriedly abandoned minutes before the party arrives. Alchemical equpment worth 350gp is sitting on tables here. In many drawers and chests around the room there can be found several useful items mixed in between wizardly junk: Potion of Healing, Wand of Magic Detection, Amulet Of Proof Against Detection And Location. Searching this room is not without risk - one of the drawers is full of yellow mold. On one of the walls there is a large number of glass balls showing sights from many invisible arcane cameras spread around the dungeon. Spot marked "Main Ball" is glaringly empty. There is one such screen for every non-secret area except room 18, leaving very few blind spots. Close examination and a successful DC15 investigation check will reveal that one of the cameras is suspiciously pointing at the wall leading to room 17.
17. By the western wall there stands a large painted statue of a demonic being with two heads, one of a goat, the other of a wolf, body and and four man-like arms holding real scimitars, legs of a spider, wings of an eagle and four ruby eyes worth 350gp each. Should it be interacted with, it animates with the statistics of two manticores without tail spikes.
18. This is the main room of Mage Delimal where he resides together with his two Tiger familiars. The only door leading here has three keyholes which must be activated simultaneously by the three numbered keys found around the dungeon. Delimal may simply pass through it as if it wasn't there. He sits on a throne by the west end of the room, behind him there is a treasure hoard containing the following: Lesser Scroll of Weapon Upgrade, Main Ball, 1000gp worth of silver coins, self portraits and monster paintings. There is a massive 10'x25' empty dining table with many chairs along it in this room as well.

Spikes - A weight-activated trap which causes thin steel spikes to strike out from holes in the floor dealing 6d4 damage to every frontliner, half on a DC14 dexterity save. Passive perception of 15 or better notices thumb-sized holes dotting the floor.
Three blades - A scything blades trap activated by pressure plate. Passive perception of 15 or better notes three thin and long seams in the wall. Deals 3d8 slashing damage, half on a DC14 dexterity save to all characters in a 10' cube, which is likely the two frontliners of the party.
Flame - A continual flame torch is attached to the wall here. It will stop working when removed. It shines bright light for 30' and dim light 30' beyond that.
TP - circular, bound teleporters. Will transport anyone stepping through to the other one.

Random Encounters:

Every time the party backtracks, spends plenty of time in a room or makes a loud noise, roll a d6, on a 1 an encounter appears. Random encounters are always Easy, whatever that means for any given party. Example encounters for 3rd level: 5 giant rats, 2 orcs, 9 fire beetles.

Homebrew Parts unexplained above:

• Belt of Gender Bending - The only effect of this minor cursed item is reversing the physical sex of the wearer. It may not be removed until a Remove Curse is cast, but thereafter it ceases to be cursed at all and may be equipped and unequipped freely. It appears as a Belt of Hill Giant Strength to identification.
  
• Rip-activated scroll - To activate this scroll one must rip it, which takes as long as the casting time of the spell and generally requires both hands.
• Robe of Powerlessness -  A horrible cursed item which appears as a Robe of Protection to identification, but actually reduces the wearers intelligence and strength to 3 and prevents them from using any of their magical powers. The robe can be removed easily, but only a Remove Curse followed by two casts of Enhance Ability will restore power to the victim.
• Something having the statistics of two monsters means doubled hit points and number of attacks.
• Mage Delimal - Stats of a Mage, possesses two portent dice, has a constitution score of 16 hence 67HP, sees all invisible things, knows all spells known by normal mages except for fireball which he replaceswith lughtning bolt, all divination spells and the following extra ones which take the form of blasting horrible insights directly into the targets brain: Mind Sliver, Mind Spike, Raulothim's Psychic Lance, Synaptic Static. He is armed with the following magic items: Arcane Grimoire +1, Robe of Protection, Scroll of Counterspell and a Potion of Heroism which he drinks to prepare for the group. He used to be a barbarian but has taken a liking to magic after touching the statue in room 9. He wears blue robes and has no hair at all, with geometric patterns and a fake beard tattooed on in its place. He has taken over this location and is currently engaged in research about how dungeons work, spying on its inhabitants via the surveilance network and performing many experiments. Even though adventurers are a natural part of a dungeon life cycle, Delimal is furious that the party dares interfere in his experiments and is willing to kill them unless they return all treasures and promise to never return. While in room 18 he has a more difficult time spying on the goings-on of the dungeon as he uses the Main Ball which observes only one chosen arcane camera at a time. His two cats are utterly loyal, never take damage from his spells and are guilty of wiping out the previous adventuring party.
• Lesser Scroll of Weapon Upgrade - This rip-activated scroll targets one non-magical weapon and enchants it to grant a +1 bonus to attack and damage rolls.
• Main Ball - This Crystal Ball is powered by an air elemental imprisoned inside. With Delimals death the enchantments binding it there fail and the sphere begins cracking, releasing the venegful spirit after three rounds. The elemental will seek to unload its rage on the closest living being, likely the PCs. With the destruction of the main ball, all arcane cameras in the dungeon cease to function.

Breakdown and Notes:

XP awards from winning encounters:

Level 3:

Gelatinous Cube - 450xp

False Ogre, 3 Orcs - 1500xp

Animated Statue traitor - 200xp

Skeleton Sniper - 450xp

6 Goblins with poison - 600xp

Otyugh - 1800xp

4 Shadows, 3 Skeletons - 1375xp

Orc with crossbow trap - 100xp

Total: 6475xp

Level 4:

Double-manticore statue - 2100xp

Mage Delimal, two Tigers - 6400xp

Air Elemental - 1800xp

Total: 10300xp

Treasure:

Level 3 - 3500gp, 8 permanent, 11 consumable, 2 cursed

Level 4 - 2400gp, 3 permanent

items counted here are those that the party is actually expected to acquire and use

You know, 5e adventurers are way tougher than the actual system math would suggest. Theorethically this is over twice the daily XP budget that the adventurers are supposed to do without long rests, but a decently built party can absolutely overcome it.