Kobold Press’ “Demon King of the Styx” (Adventure Review)

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Over the past few years, we’ve seen a number of new digital-only one-shot adventures from Kobold Press that are compatible with both D&D 5e and their fledgling Tales of the Valiant system. The idea is to offer up short, satisfying, standalone modules that can be run over a few sessions or dropped into an existing campaign.

The latest offering is Demon King of the Styx, an adventure designed for Level 6-7 characters that features corrupted rivers, vengeful dwarves and twisted demons. While technically, the adventure is part of Kobold Press’ larger Labyrinth setting for Tales of the Valiant, it’s also flexible enough to be dropped into just about campaign world. You can pick it up now as a PDF for $4.99 USD from Kobold Press or DriveThruRPG.

So is this trip down the Styx worth taking? Below, we paddle into all the details.

What is the “Demon King of the Styx” adventure?

Demon King of the Styx is a 25-page digital-only adventure compatible with Tales of the Valiant and D&D 5e that’s written by longtime Kobold Press contributor Philip Larwood.

The adventure is designed for Levels 6 to 7 characters and begins in the small fishing village of Stillwater, where the nearby river has mysteriously begun to dry up, taking the villagers’ livelihoods along with it. After the PCs arrive, they soon discover that the area is linked to the fabled River Styx, and that a dark corruption is spreading across the land.

Players are then tasked with finding out who (or what) is damming the river, with the journey putting the heroes in contact with a twisted dwarven alchemist, corrupted swamp monsters and an ancient evil from the underworld.

It’s a formulaic set up that feels familiar, yet there are some interesting twists and turns, not to mention unique environmental challenges and a some genuinely creepy monsters. In fact, the book features two new monster stat blocks that only appear in Kobold Press’ Monster Vault 2. It also includes a new magic item, detailed maps and a random encounter generator, all of which offers at least a few sessions of play (my group and I spent three, short sessions on it)

Where Demon King of the Styx really shines, however, is just how easy it is to set up, with Kobold Press walking GMs through the major story beats and NPC motivations, and offering advice on how to set things up and handle major encounters (Wizards of the Coast and other D&D 5e third-party publishers could learn a thing or two from Kobold Press when it comes to actually providing table-useable content). It’s also worth noting that for a short, standalone adventure it has some amazing artwork and the accompanying maps and dungeons are incredibly well designed.

Is “Demon King of the Styx” worth running?

Pros

• A classic yet flexible premise: The village-in-trouble setup is a classic D&D trope, and it still works well here, in addition to offering players a bit of choice in terms of how they want to complete their mission.
• Lore integration: The adventure does a great job of tying in the mythology of the River Styx, and even opens the door for taking the players deeper into the Tales of the Valiant Labyrinth setting if they’re so inclined.
• Dynamic finale: The climax is solid, with high stakes and dramatic choices, offering players and GMs a satisfying ending without feeling like they’ve been railroaded.
• Useful new content: There’s plenty of solid stat blocks (including two brand new monsters) and a surprisingly unique magic item.

Cons

• Limited roleplay variety: Most of the adventure’s encounters lean toward combat or survival challenges, leaving fewer opportunities for extended social interactions or mystery.
• Mid-tier level range: Characters below level 6 will struggle with the adventure’s high-CR creatures and environmental hazards, although with a bit of tinkering you might be able to lower or increase the difficulty for other tiers of play.
• Linear travel sequence: The travel sections, while flavorful, can feel straightforward if you don’t add some interesting encounters (the book does provide a random encounter table, but you’ll likely want to do some extra legwork).
• Villain motivation: The villains aren’t exactly the most original and are little two-dimensional, but as a GM you can likely add a bit more depth to them if you’re up to it.

Final Thoughts & Review Score

Demon King of the Styx is a well-crafted mid-tier adventure that delivers a satisfying mix of dark fantasy atmosphere and high stakes. While it doesn’t reinvent the wheel narratively, its pacing, structure and dungeon design are all top notch. If you’re looking for a decent one shot with exploration and combat with an environmental twist, this is one trip upriver that’s worth taking.

Final Review Score: 18 out of 20

You can pick up Demon King of the Style PDF now for $4.99 USD from Kobold Press or DriveThruRPG.