This week’s encounter is Sanctum of the Reptile God, an all-out, life-or-death fight to the finish. In this encounter, the characters must defeat Explictica Defilus, a spirit naga whose evil has echoed through legend for generations. Aiding the so-called “Reptile God” are her faithful cultists, who have used her mystical powers to craft an alchemical curse that they intend to spread across the land. The price of failure is more than just death—if the revived cult of the Reptile God is allowed to infect the land with its hex-plague, all living beings across the realm could be transformed into scaled abominations.
Adapting this Encounter
If you want to run this fight as a standalone encounter, the characters could simply stumble across the cult’s base of operations while exploring the wilderness, like a player might stumble across a dungeon in an open-world adventure RPG. Alternatively, you can insert this encounter into a dungeon to serve as a minor boss fight, or you can adapt its story to serve as a major boss fight for a dungeon or dungeon level. Since Explictica Defilus is worshiped by her cult as a “Reptile God,” a dungeon that features this encounter could be inhabited by lizardfolk, behirs, giant lizards, froghemoths, medusas, and wyverns.Yuan-Ti are suitably reptilian adversaries, but are the hated rivals of nagas like Explictica. She may keep yuan-ti as slaves or as grudging allies, but the two will never see eye-to-eye.
However, you can also adapt this encounter to fit into a longer adventure or campaign. This tactical combat encounter takes place in an arena excerpted from a map in Tomb of Annihilation. While this encounter is unrelated to that adventure, it could serve as the climactic battle of this adventure, with a bit of modification. You could do so by replacing the Death Curse with the cult’s Hex-Plague of Scales, and removing the Tomb of Nine Gods from the adventure entirely, or by making the tomb optional “post-campaign” content. This situates Explictica Defilus as the adventure’s main villain, and focuses the adventure entirely around reaching the City of Omu and defeating Explictica.
Combat Encounter: Curse of the Reptile God
This combat encounter is a tough-as-nails encounter for a party of four 9th-level characters. Similarly, this combat will serve as a challenging but typical encounter for a 10th-level party, and a mere speed bump for an 11th-level party.
A hidden temple to a cruel and calculating monster is secreted away somewhere in the wilderness. A cult has gathered around the temple, worshiping its mysterious master as an all-powerful Reptile God. The master of the hidden temple has been called that name before, though she is no god. Explictica Defilus, a spirit naga of unfathomable cruelty and hatred, was once worshiped as a god in ages past, but her cult was crushed by a group of adventurers. But a naga as powerful as Explictica Defilus cannot be killed by mere adventurers. Though her cult was crushed, her spirit was reborn in a matter of days, and she set out to start her fell work anew.
She bent evil people to her will, but in time she was defeated again. And again, and again, and time after time the naga’s work was undone by mortal beings. Explictica, immortal and seething with hatred for all mortal life, has assembled a new cult of lizardfolk—and humans willing to become part of her “superior, scaled race.” She is worshiped as the Reptile God again, and has falsely claimed to bestow immortality upon her humanoid followers, at the price of becoming one of the lizardfolk. With her followers’ aid, the naga has brewed a concoction that could be used to poison all waterways in the realm—and all who drink the accursed draught will soon succumb to the Curse of Scales, and become lizardfolk, just like the fools who willingly drank the brew themselves.
The characters enter the sanctum of the Reptile God, perhaps aware of the power of its master, perhaps not. Dimly lit and filled with the hissing chants of Explictica’s cultists, the sanctum must be instantly recognized as a place of danger and evil deeds. The silky voice of the Reptile God herself soon wends its way into the adventurers’ ears, drifting melodically over the rhythmic chanting of her cultists. She promises them power, wealth, and family—if only they would sacrifice their flesh, free will, and mortality, and become one of her lizardfolk.
If the characters refuse, as she expects, her cultists attack while she hurls spells at them from afar.
Sanctum of the Reptile God Features
This chamber has the following features:
Accursed Pool. A pool of seething red liquid drains from behind Explictica, into a pool around her balcony, and then into a central pool. Any creature that drinks or is submerged in this liquid must succeed on a DC 17 Constitution saving throw or be poisoned for 1 minute. It can repeat this saving throw at the end of each of its turns, ending the effect on itself on a success. If it is poisoned in this way for a full minute, it is afflicted by the Curse of Scales and falls unconscious for 24 hours, during which time it is transformed into a lizardfolk. A remove curse spell can break the curse before the transformation is complete, but only a wish can permanently reverse the transformation.
Elevation. Explictica’s balcony is 40 feet above the floor of the chamber. The raised platform in the west of the room is 30 feet above the floor of the chamber. The southern half of the sanctum is 10 higher than the floor in the northern half.
Ceiling. The sanctum’s cavernous ceiling is 100 feet high. All eight pillars in this room reach from the floor to the ceiling and are covered in spiraling, serpentine designs.
Creatures. The sanctum is inhabited by the following creatures: Explictica Defilus, a spirit naga, who lounges upon her balcony on the north end of the room. Four lizardfolk cult fanatics, two of whom stand on either side of Explictica, and two who hide behind the two northernmost pillars. Four lizardfolk thugs, who hide behind the middle four pillars. One bone naga, a wretched and mutated skeletal creature was created when a treacherous cultist was bound and thrown into the central pool; it now lurks within the pool and is bound utterly to Explictica’s will.
Gong. A massive brass gong covered in reptilian designs stands on the raised platform in the west of the room. Once per day when a creature rings it, the creature casts animal friendship upon all reptilian beasts within 120 feet of it that can hear the gong (save DC 16).
Light. The sanctum is pitch black, save for a brazier of burning coals in the southern end of the room, which casts bright light in a 10-foot radius and dim light for 10 more feet. Several blue-green motes of magical light float along the walls, when the cult’s humanoid members are present, but Explictica Defilus can cause the lights to turn on or off as a bonus action. She douses them the instant she learns that adventurers have entered her temple.
Scale. This map uses 10-foot squares.
Treasure. Explictica sits curled about a great mound of treasure, made of offerings and tithes, as well as plunder. This treasure is equal to a challenge rating 9 treasure hoard.
When the characters enter the sanctum from the passage to the south, read or paraphrase the following:
The sound of rhythmic hissing grows louder and louder as you walk down the stone passage, until you emerge from the hall into a wide chamber choked by shadows. Then the hissing stops, and the chamber is eerily quiet; only the faint sounds of bubbling water, crackling embers, and the breathing of a dozen unseen figures can be heard.
Before you is a brazier filled with burning coals. Further ahead, its light glints off a vast basin filled with seething crimson liquid, which seems to pour from the head of a massive stone serpent. Then a voice breaks the silence.
“A group of mortals have entered my sanctum. What say we to mortals, my faithful?”
The voice is answered by a chorus of hissing chanting.
“Do not be afraid. You are speaking to a god. A god of all things scaled and slithering. I have welcomed many mortals into my fold over the years. They have willingly shed their flesh and their mortality and become my undying, scaled faithful. My people are strong. They are unafraid. They are unhindered by emotion, sentimentality, and other pesky mortal weaknesses. I plan to share this blessing with the entire realm, mortals; shall you drink deep of it now, and pledge your loyalty while you are of sound mind? Or shall you be made to drink unwillingly, and find my blessing through pain?”
Explictica Defilus is happy to humor any adventurers who wish to talk, negotiate, or barter. She refuses to budge an inch, and will let her mortal visitors prattle on as long as they want. She responds in terse, self-aggrandizing answers, fully expecting the characters to attack at any moment. She allows the characters to advance to the edge of the pool to drink from it, but the moment any of them wander beyond, she barks out a warning. “Come no closer! Take another step, and perish.”
If the characters choose not to heed this warning, Explictica and her cult attacks.
Explictica Defilus seeks to divide her foes and defeat them one by one. Her cult follows her orders unerringly, and she uses them as cannon fodder to prevent her foes from reaching her balcony.
On the first turn of combat, the thugs hiding behind the middle four pillars burst from cover and charge the characters, yelling a bestial war cry. The two cult fanatics beside Explictica cast hold person, while the two on the ground cast spiritual weapon and sacred flame, favoring paralyzed targets. Explictica casts dominate person on any character unaffected by her cultists’ hold person spells, and commands the character to slay their former allies, starting with arcane spellcasters.
On subsequent turns, the two cult fanatics on the balcony use spells like command and hold person to try and stop the characters from approaching them, if possible. If they successfully paralyze a target with hold person, they hide behind Explictica to prevent their concentration from being broken. The thugs and the fanatics on the ground use every attack or spell at their disposal to deal damage to the characters. They avoid dealing damage to any target dominated by Explictica.
Once Explictica has dominated an enemy, she prefers to use lightning bolt to deal damage to her enemies from afar. If at least half of her cultists are defeated, she calls for the bone naga lurking in the central pool to arise and defend her. The bone naga casts spells as if it were a spirit naga in life, and uses hold person and lightning bolt as its primary methods of attack. If her enemies ever get close to her, she uses dimension door to warp to the southern entrance to the sanctum and flees.
Fall of the Reptile God
If Explictica is defeated, she roars that she will never be truly defeated, and her cultists and her bone naga fight to the death to avenge her. Explictica is right; thanks to her powers of Rejuvenation, she will be restored to life in 1d6 days, and will use all the powers at her disposal to make sure the characters pay dearly for embarrassing her.
Spoiling the Brew
Explictica may return in time, but the characters have the chance to spoil years’ worth of effort by destroying the Hex-Plague draught the cult planned to use to spread the Curse of Scales. A character that makes a successful DC 17 Intelligence (Arcana or Religion) check learns that the plague can be temporarily neutralized for 1d10 days by casting greater restoration upon the brew, but a creature with a power equal and opposite to Explictica’s—a guardian naga—can permanently neutralize the plague. Finding such a creature could lead the characters onward to another adventure.
The Cult’s Return
Obviously, Explictica’s cult was made up of more than eight cultists. The others are lurking in villages across the realm, secretly spreading word of their god and goading others into drinking their tiny vials of the Hex-Plague draught. If the brew was not spoiled by the time Explictica rejuvenates, she commands her cultists to return to her sanctum and begin spreading the plague immediately. If the plague was destroyed, she commands her cultists to hunt down the characters and guide her to their location. The consequences of her vengeance are yours to determine.
Did you like this adventure? You can pick up more adventures I've written on the DMs Guild, such as The Temple of Shattered Minds, a suspenseful eldritch mystery with a mind flayer villain (for 3rd level characters). My most recent adventure is in Dragon Heist: Forgotten Tales, a book by the Guild Adepts which gives you a new beginning, middle, and end to Waterdeep: Dragon Heist. It's the perfect way to give this adventure even more replay value! My new beginning is a great way to introduce a campaign focused on either the drow or devil cult factions causing trouble in Waterdeep.
If you want Adventurers League-legal adventures, take a look at The Cannith Code, set in the magic-punk Eberron campaign setting, All Eyes on Chult, a high-stakes adventure set in Port Nyanzaru included in Xanathar's Lost Notes, or Fire, Ash, and Ruin, a demon-filled dungeon delve in an active Chultan volcano! This post contains DMs Guild affiliate links, which means that I—James Haeck—get an extra 5% of the sale if you buy anything from the DMs Guild using these links. You don't pay any extra, but your purchase helps support my work. Thank you so much!
Also, for more free encounters, take a look at the other encounters in the Encounter of the Week series!
James Haeck is the lead writer for D&D Beyond, the co-author of Waterdeep: Dragon Heist and the Critical Role Tal'Dorei Campaign Setting, the DM of Worlds Apart, and a freelance writer for Wizards of the Coast, the D&D Adventurers League, and Kobold Press. He lives in Seattle, Washington with his partner Hannah and their feline adventurers Mei and Marzipan. You can usually find him wasting time on Twitter at @jamesjhaeck.