Kobold Press Goes Dark With ‘Underworld: Sunless Depths’ Kickstarter

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Kobold Press is heading back into the darkness with a brand-new TTRPG project entitled Underworld: Sunless Depths. Fully compatible with both D&D 5.5E and Tales of the Valiant, the project includes two books: a supplement geared towards both players and GMs that features new subterranean character options, mechanics and monsters, and a standalone campaign book that takes players from Levels 1 to 12.

The books, however, will first be brought into the light via a crowdfunding campaign, which runs from now until October 9th on Kickstarter. Below, we go deep into all the details.

What is the Underworld sourcebook about?

The book is a new D&D 5.5E and Tales of the Valiant-compatible supplement that explores the Underworld (which is essentially Kobold Press’ take on Dungeons & Dragons’ Underdark), a sprawling, lightless world located deep below the earth that’s filled with ancient kingdoms and sightless horrors lurking beyond the reach of daylight. Like other major Kobold Press supplements, the book is geared toward both Game Masters and Players.

Notably this isn’t the first time Kobold Press has explored the Underworld, with the publisher also releasing the 2020 Underworld Player’s Guide for D&D 5E (which featured a range of subterranean player options) along with the GM-focused Underworld Lairs (which featured a range of unique locations).

Player Content

The 2026 Underworld sourcebook includes the following player-facing options (although this may change based on stretch goals):

• 6 Subclasses: The Mycetic Druid, Mechanist Gemologist, Magnetist Mechanist, Dowser Ranger, Ambuscader Vanguard and Sunstaff Wizard.
• 3 Base Lineages: Crystalline, Mushroomfolk and Lizardfolk
• 2 New Variant and Expanded Lineages: Burrow Beastkin and Cave Dragonborn
• 5 Heritages: Darkshore, Fiendbound, Mycoculture, Vassal and Warrenborn
• 4 Backgrounds: Gem Cutter, Miner, Stonemason and Wilderness Guide
• Talents: A dedicated progression section offering specialized talents to customize subterranean adventurers.
• Magic Items: Covering both standard magic items and high-tier Fabled Items.
• Spells & Rituals: A range of spell options covering a wide range of schools, classes and tiers.

Game Master Content

For GMs looking to run Underworld adventures, the book includes:

• Survival Mechanics: New rules for handling suffocation, cave-ins, navigation without light and environmental hazards.
• Ruin Site Generator: Random tables to generate underground ruins on the fly by Theme, Size, Style and Purpose.
• Infamous Ruined Realms: Pre-built delve locations including Cleithrum (a sunken and cursed capital of the sahuagin) and Dauranosk (a ruined city of the brain-devouring beings).
• Cavern Bestiary: A range of new monsters across Challenge Ratings, along with with creature templates like Abyssal, Subterranean and Worm-Ridden options.
• Factions & Settlements: Detailed lore and frameworks covering deep empires, subterranean enclaves and competing Underworld factions.

What is the Underworld: Descent into Darkness campaign book about?

The book is 10 chapters in length and contains a complete Level 1 to 12 campaign that’s compatible with both D&D 5.5E and Tales of the Valiant.

The campaign takes players from the surface into the depths of the Underworld where they must navigate between various deep-dwelling factions, explore forgotten abyssal ruins and stop a rising subterranean terror before it breaks through and consumes the world above.

What are the backer options?

While the primary draw of the Kickstarter is the two supplements (both of which come in deluxe print versions), there are also a range of accessories including poster maps, player handouts, GM screen inserts and cardboard monster pawns. The backer tiers include:

• Digital PDF Tiers (~$25 USD): A PDF of either the Underworld: Sunless Depths setting sourcebook or the Descent into Darkness campaign book.
• Double Digital PDF Bundle (~$40 USD): PDF copies of both books, along with digital map packs.
• Standard Hardcover + PDF (~$50 USD): The physical hardcover edition of either book along with the associated PDF.
• Dual Hardcover Delver Bundle (~$95 USD): Both physical books in standard hardcover format, with PDFs of both titles.
• Limited Edition Collector’s Hardcovers (~$100 – $130 USD): A deluxe printing of either book, featuring foil-stamped faux-leather covers, custom endpapers and ribbon bookmarks manufactured specifically for the Kickstarter.
• Survivor’s Kit Physical Bundle (~$175 – $200 USD): Pairs both core hardcovers with the physical Underworld accessory pack, containing cloth/poster battle maps, player handouts, GM screen inserts and cardboard pawn collections.
• Deluxe All-In Collector’s Vault (~$300+ USD): The complete physical and digital run, including limited edition collector hardcovers of both books, the full Survivor’s Kit and VTT versions.

Notably, if you back the project, you can also enter an official contest to submit an adventure, which you’ll be paid for and which will be officially published by Kobold Press.

Final thoughts

Subterranean adventures have been a staple of TTRPGs since the earliest days of the hobby, and still remain popular over 50 years later. In fact, official D&D itself seems to be heading back to the Underdark given some of its recent Unearthed Arcana playtests. These new Kobold Press books, however, are here now and look like they’ll be shining a new light into the darkest depths.

We’ll be keeping a close eye on this project in the days ahead and will be doing a complete review of both books once they’re available to the general public. In the meantime, you can back from the project from now until October 9th on Kickstarter