An Adventure Hook Written By: Dice Prophet
Type: Dungeon Crawl, Bug Hunt, Comedy
System: D&D 5th Edition or Pathfinder
Ideal Party Size: 4-5
Recommended Levels: 3-6
This adventure is a twist on a common side quest: exploring the sewers! The deep and dark places of the world are often chock full of the same predictable beasts, such as spiders, rats, and the occasional ooze creature. But what if the sewers were suddenly flooded with the contents of an alchemist’s laboratory?
Alchemists are the mad scientists of the adventuring world; they concoct the powerful and often unstable compounds that can give adventurers the edge they need to survive. By simply imbibing an alchemist’s brew, one can be healed of all wounds, protected against most damage, granted the might of an bull, or given the agility of a cat. Alternatively, a tiny bottle could also hold the most potent toxin, an acid that could eat through stone, or an explosive surprise. Now imagine what would happen to the conventional subterranean ecosystem if all denizens were suddenly exposed to a wave of miscellaneous potions, oils, and extracts! It would be absolute madness!
That is where the quest begins. A local alchemist has been mindlessly dumping their failed experiments, excess reagents, and miscellaneous mixtures down the drain. This had the unfortunate side effect of contaminating the usually docile vermin that inhabit the sewers. Magically modified creatures have begun to emerge at an accelerated rate, terrorizing the populace. Chaos bubbles up from the depths, and those brave enough to venture underneath and purify the corruption can prevent trouble from spilling over!
Read the following flavor text to the player characters at the beginning of the quest:
“Weeks ago, an alchemist’s lab was raided and quarantined by the local authorities. The owner had been illegally dumping their reagents into the general sewage system in an attempt to circumvent proper magical disposal methods and shave off costs. The resulting cocktail of magical-imbued chemicals has altered the denizens of the underground, turning them into dangerous, never-before-encountered monstrosities!
Although the origin of the contaminants have been stopped, there has been no decrease in the appearance of mutated creatures emerging from the sewers and wreaking havoc! A massive reward is promised to adventurers strong and courageous enough to investigate the source of the ongoing infestation.”
Denizens of the Deep
The basic template for every encounter is simple: take a commonly-used subterraneous monster, and modify it by applying an alchemical compound.
Perhaps the players encounter some rats, but they’ve recently drank Potions of Invulnerability and must be avoided until the effects wear off. An alligator may have accidentally imbibed a Potion of Flying, and is now hovering through the corridors, snapping at unsuspecting prey. The players could get stuck inside a Gelatinous Cube, but the acidic properties have been completely neutralized by the presence of a powerful base, and the creature poses more of a locomotive hindrance than a threat to their well-being.
Experiment with whatever combinations are suitably hilarious or mechanically interesting, to keep the players guessing on what they will have to fight next. But try to not repeat combinations.
Like most sewers, any water sources found are either fetid, diseased, or downright deadly to the touch. They may also obscure whatever enemies the players will face, whenever appropriate.
However, some pools can also be saturated by helpful compounds. Perhaps one of the levels have been entirely flooded, but the water contains so much Potion of Water Breathing that it is literally impossible to drown in it. The contamination can be both a benefit or a hindrance to the party, depending on whether or not they can correctly identify the liquids they find.
The Toxic Dragon
At the lowest depths of the sewers there is a creature that is a living amalgam of all the contaminants. This putrid mass of caustic material takes the form of a large black four-legged beast with translucent green wings. The toxic dragon viciously prowls the dark, consuming all that it can catch and spewing forth more mutated terrors from its body. This creature is the newfound source of the contamination.
The toxic dragon awaits at the deepest level, and serves as a final boss for the dungeon. In regards to monster design, it is mechanically a Black Pudding, with the same hit points, properties, and defenses. But also possesses the physical appearance and locomotive abilities of a Black Dragon Wyrmling, and displays animal-like intelligence. Like any creature, it will defend itself and its lair ferociously. Tactically, it seeks to kill and consume rather than negotiate or take prisoners.