Treasures of Deep Grotto
The Sunken Condition
There’s a mechanic in D&D that is prominent on the character sheet, changes every level, and yet, I constantly found even more experienced players forgetting what it was. I set out to fix that, and give games a new way to play.
“When a character gains the Sunken condition, the tether to their soul is at risk. The strength of this tether is represented by their hit die. If a character has 0 hit die when they are reduced to 0 hit points, they die.”
Suddenly, Hit Dice matter. Magic items offer power at the cost of your soul. Traps drain your life force. Puzzles force meaningful choices. Every Hit Die spent is a step closer to death.
The Mechanic
Deep Grotto is a five-room dungeon. Players start already dead, their ship destroyed by Captain Grimscar. A Sea Gnome revives them, though their actual souls are trapped with Grimscar.
Each room teaches the Sunken Condition:
The Coral Chamber
Pay one Hit Die to get a runic mark. Voluntary sacrifice, low stakes.
The Watery Chamber
Pay another Hit Die, or refuse and trigger a trap that forces harder choices. Refusing costs more than paying ever would.
The Sanctuary
Fight Grimscar and a statue of Y'gathul that drains Hit Dice every round via lair actions. Players must decide. Destroy the statue first and make the fight longer, or burn through their souls to try and end it fast?
Win, drink your soul from a vial like a potion, live to sail another day.
The Adventure
I designed four original subclasses compatible with D&D 5th Edition: the Buccaneer Fighter, the Mist Breaker Ranger, the Spellskin Wizard, and the College of Tide Song Bard. I also created magic items and tattoos, some of which offered power at the cost of Hit Dice, reinforcing the resource mechanic throughout play. These were designed to make players engage with the core design challenge of the adventure.
Player Options
Hit Point Press published Deep Grotto for Free RPG Day 2023. We printed 20,000 physical copies distributed worldwide, plus thousands more digital downloads. I ran it at game stores, signed copies, streamed it on actual plays.
The Sunken Condition became the foundation for SINK!. It appears in magic items, class features, and environmental hazards throughout the setting. Deep Grotto proved the mechanic worked at scale and became the catalyst for our $280,000+ Kickstarter, and has been revised as the first adventure in the campaign.
Beyond the One-shot
The Sunken Condition was my solution to a problem that was right there the whole time. Hit Dice rarely matter, so I made them matter. That simple reframe opened up design space big enough to build an entire setting around.
But Deep Grotto also taught me about dungeon design at scale. Running it for dozens of groups, strangers at game stores, streamers, convention tables, showed me how different player types approach the same puzzles. Some immediately understood the risk and reward. Others needed the trap to teach them. Watching that variety helped me design better boss mechanics, clearer quest hooks, and more intuitive progression systems.