This is a mostly complete write-up for a dungeon adventure I’m running for my regular group. It’s somewhere between a “finished” adventure and the brief notes I typically run with. I often skip writing up descriptions, but I had a lot of fun writing up some extra flowery exposition.

The Obsidian Heart

Background

This place was created by Elena Hexwalker to protect the Codex Gnosis (a key to the plane that “Contains all Knowledge”). She’s kind of a big player in my world: she helped unify the Kingdom of Idreal, created the Dragonborn, founded a university of magic, etc.

The acrid scent of magic lingers here, the hairs in the back of your neck stand up, energized by the arcane atmosphere. The walls are made of a common dark gray stone, but the floor is made of polished black glass, any light you create here if reflected in the floor, but you cannot see your reflection in it.

Maps created with Dungeon Scrawl — used under CC BY 4.0 license.

1 The Bottom

You descent from an open hole in the ceiling down into a floor made of black glass. The floor and walls are stained with guano. On the ground near the north wall is an inert Iron Golem, its body and limbs pitted with rust, about it lay a few old moth-eaten corpses. The ceiling is crowded with swarms of stirges.

Roll Initiative for the 2 Swarms of Stirges. The skeletons belong to travelers who followed the corpse in Room 3, fought and defeated the Golem, then fell to the stirges.

2 The Deep

The south half of this chamber is overtaken by a pool of cold water. There are scattered fish bones around the edges of the pool. A thick mineral scent mingles with the air here.

A successful perception check will let the players hear that the water is moving, and therefore goes somewhere. The tunnel is too small for most players, but a transformed Druid or maybe a wizard’s familiar could make the journey. If the party ventures too close to the edge of the pool, they may be attacked by the Grell that dwells within the water. Once the Grell is bloodied, it will flee into the secret passage.

2a Secret Passage

Cold water assaults your senses, your extremities immediately begin to lose sensation as you drag yourself into this tight, cramped space. It seems like the walls press down on you, clamping you into the dark, instantly disorienting you. Your mind is drawn to the pressure of a thousand tons of earth above confining you into a frozen, breathless, tunnel. For a moment, you consider that you will never escape here before you pull and worm yourself further into the sharp glass teeth of this hellish black maw.

This tunnel is sized for a tiny creature, but may be squeezed through. Each round inside, a squeezing creature takes 1d3-1 slashing damage from the sharp edges in the walls. At the corner, there’s sinkhole current. Make an Athletics check (DC 14) to avoid being drawn into the Underdark. (Have to fail twice in a row, first round 1d6 bludgeoning damage). In addition, the Grell may ambush at any time. Assuming the character squeezing through needs to breathe, each time they take damage, they must make a Concentration check to hold their breath if they fail, they begin to drown

3 Ooze Town

The north-west corner of this room is occupied by a pool. The walls and obsidian floor are coated in greenish slime. Against the far wall there is a humanoid skeleton clothed in rags with a backpack next to it, a light shines from its lifeless hand and its shattered legs are extended in front of it.

There are 1d4 Psychic Gray Oozes on the ceiling here. The skeleton is a traveler who fell down the hole into the dungeon, broke their legs, crawled away from the stirges and fell asleep here only to be eaten by oozes. Loot: 2 potions of healing, +1 buckler, Adventurer’s Ring

4 Opal Trap

In the far wall is a deep-set alcove with thumb-sized holes around it. There is a plaque below the alcove that reads: I cannot be held, confined to a vision, yet touch all deeply. What am I? Inside the alcove is a large opal gem.

The answer to the riddle is “Beauty” (which is itself a hint about the placement in the final puzzle), or anything else you find acceptable. If the players reach into the alcove to take the gem without answering the riddle, spikes will try to trap the player’s arm.

5 Obsidian Golems

The scent of magic lingers especially heavy here. This room has entrances to the south, east and north. On the far western side of the room is an inscription.

If the party crosses the room to inspect the inscription, Obsidian Golems will form out of the floor and attack (or DC 17 Stealth Check to avoid). 3-4 Glasswork Golems (with Vulnerability to Bludgeoning and Thunder) One of which has a Lead Coin with a Column engraved in its chest If the party casts spells here, the innate arcane energy in this chamber will rebound (roll for Wild Magic). The inscription is written in Draconic. It describes gemstones and metals in terms of their alchemical and theurgic/philosophic properties.

6 Basilisk Nest

This chamber is the end of the passageway, at the far end water drips from the ceiling into a tiny dish formed into the floor underneath, creating a pool the size of a small bowl. In the left there is a bed made of small stones and crushed gravel, apparently dug out from the walls here. On the bed, a pair of crocodile-sized lizards with aquamarine crystals growing out of their backs sleep.

2 napping Basilisks, (engineered to maintain the obsidian floor). Loot:

• Stonespeaker Crystal (in the Nest)
• Potion of Longevity (from the dripping water)

7 The Throne

A throne in Ptolisian (Dynastic Egyptian) style greets you from across the way. An imposing warrior wrapped in linen and wearing a headdress of gold thread with a Jade pendant at the forehead sits upon it, a Draconic snout and blue scales peak underneath its linen covering. To the left, there is a door with a carving and various stones and coins inlaid. On seeing you enter, the figure rises and lets out a dry exhalation. Roll Initiative!

Vazirax will begin the fight without using his greatsword, he is for the most part mindless at the begining of the fight. Once he’s bloodied, his memory begins to awake and he draws his sword and begins to use his sword.

7a The Gate

The Door is inscribed with the Quaballistic Tree of life (example below) with the following gems and metals.

• 1: The Crown — Gold Annulet
• 2: Wisdom — Sapphire
• 3: Understanding — Tin Owl
• 4: Mercy — Spinel
• 5: Severity — Iron Square
• 6: Beauty — Missing (Opal found in the alcove in room 4)
• 7: Victory — Bronze Eagle
• 8: Splendor — Citrine
• 9: Foundation — Missing (Lead Column in the Golem’s chest)
• 10: Kingdom — Missing (Jade in the Mummy’s headdress)
• 11: Individuality — Blood (appears after the others as a blood-stained circle) with the following inscription:

Cold when detached, hot in anger. I quench the cruel and flow through kin. What am I?

If the players need a hint (likely unless you have a particularly esoteric group). A DC 15 Arcana Check will reveal the definitions and order of the locations. Hopefully the pattern of metals on odds and gems on evens helps.

8 The Codex Gnosis and a Poison Gas Trap

The eastern side of this room is dominated by a shallow ingress of water. There is a pedestal on which sits a metal sphere of interlocking filigree. The silver arches and swirls dance and draw your eyes almost hypnotically.

The pedestal is trapped, the door will close, and poison gas will begin to fill the air. A successful DC 18 Investigation check will detect it, a DC 16 Sleight of Hand/Thieves’ Tools check will disarm it.

As you lift your prize, a clatter sounds from the hallway behind you as the gate seals shut. Noxious scents fill the air as vents open above you spill out green-yellow mist.

At the start of each turn, make a DC 15 Constitution Saving Throw or you take 1d4 poison damage. Each time you fail, your speed is reduced by 5 ft., and you are poisoned until you leave the affected area.

The door is locked, DC 15 Athletics to break it down, or Sleight of Hand/Thieves’ Tools to pick the bypass the mechanism.

Custom Monsters

Vazirax

Blue Dragonborn Mummy based on Flee Mortals! Tuned up to be a solo boss for 5th level. CR 6.5-ish.

Immunities: Damage — Necrotic, Poison Conditions — Blinded, Charmed, Deafened, Exhaustion, Frightened, Poisoned

Resistances: Damage — Lightning

Flammable. Whenever Vazirax takes fire damage, they take an extra 5 (1d10) fire damage.

Senses Blindsight 60 ft., Passive Perception 12 Skills Arcana +2, History +2, Religion +2 Languages: Common, Draconic

Traits

• Flammable. Whenever Vazirax takes fire damage, they take an extra 5 (1d10) fire damage.
• Mummy Dust. Whenever Vazirax takes piercing or slashing damage, each creature within 5 feet of them takes 4 (1d8) poison damage.

Actions

Multiattack: Vazirax makes two Desiccating Slam attacks and uses Guardian Curse.

• Desiccating Slam. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 3) bludgeoning damage. Until the start of Vazirax’ next turn, the target’s speed is reduced by 10 feet and the target can’t regain hit points.
• Guardian Curse. Vazirax calls down a scourge on one creature they can see within 60 feet of them. The target must succeed on a DC 13 Wisdom saving throw or be cursed. While cursed in this way, whenever the target takes damage, they take an extra 3 (1d6) necrotic damage that can’t be reduced in any way. The curse lasts until removed by a cure ailment power, a remove curse spell, or a similar supernatural effect. A target who succeeds on their saving throw is immune to the Guardian Curse of all mummies for the next 24 hours.

Bonus Actions

Misty Step (re-flavored to sand)

Villain Actions

(Each once per encounter, as a reaction at any point in Initiative)

• [ ] Dreadful Glare. Wisdom Saving Throw: DC 14, one creature Vazirax can see within 60 feet. Failure: 9 (2d6 + 2) Psychic damage, and the target is Paralyzed until the end of Vazirax’ next turn.
• [ ] Last Rites: All enemies within 30 ft. make a DC 14 STR Save or are knocked Prone and take 2d6 Bludgeoning damage.

Battlefield Actions

Breathweapon Scarabs (Recharge 5-6)

• The Tell (happens at the end of Vazirax’ turn): Deep inhale, drawing the head back and you can see the scarabs moving underneath his wraps.
• To interrupt: Deal 50 damage
• The Result (happens at the start of his turn): Vazirax opens his mouth and desert beetles spill out. Summon 1d6 Scarab Swarms (1d3 if he was Interrupted) within a 15 foot cone of Vazirax. They may attack immediately, then are added into initiative.

Bloodied

When Vazirax becomes bloodied: his original breathweapon will awaken, and he will also draw his sword.

New Multiattack:

Vazirax makes two greatswrod attacks and uses his breathweapon.

• Greatsword: Melee Weapon Attack: +6 to hit, reach 5ft. one target. Hit: 11(2d6 + 4) Magical Slashing damage. Until the start of Vazirax’ next turn, the target’s speed is reduced by 10 feet and the target can’t regain hit points
• Breathweapon: DC 15 DEX Save or 3d10 Lightning Damage. Either 30 ft line, 15ft cone or 10ft emanation.