Dead Reckoning is the official expansion companion for X Marks the Spot, published by Penny Blood Adventures. Every chapter is self-contained and tagged by impact level — add a single ghost pirate faction or stack every module at once depending on how much chaos your table can carry. X Marks the Spot runs a tight three-night race. Dead Reckoning makes the island deeper, stranger, and far more dangerous. Two new factions join the race. The Remnant are ghost pirates — Captain Hollow Marrow's crew reached the Vault a century ago, claimed the treasure, and didn't leave before dawn. Now they're cursed to race every hundred years, able to reach the hoard but never touch it. They need a living proxy. They'll offer route guidance, ghost ship passage, and combat support. All they ask is three words when you claim the treasure. The catch is what happens if you don't. The Undertow Syndicate serves something older than the Lich Admiral — an aboleth sleeping beneath the skull. They don't want the treasure. They want to wake their master. Their arrival adds a Resonance tracker, a secret fourth route through flooded depths, and a catastrophic ending if no one stops the ritual. New mechanics reshape how factions interact. A Parley System lets players negotiate alliances and betray rivals with mechanical teeth — attitudes tracked from Hostile to Allied. Mutiny Mechanics let players destabilize rival crews from the inside and recruit individual NPCs. A Crew Roles system gives each player a spotlight ability tied to the race itself. The Lich Admiral's Logbook surfaces as a discoverable artifact with entries revealing the island's true history and a dark ritual that grants power at a price. Memory Echoes drop lore scenes at key locations with no Tick cost — the island shows players what happened here before. New threats scale from ambush encounters to campaign-enders. Tide Revenants are modular undead with six variants and a rising tide mechanic. The Bone Kraken is a CR 18 sea monster with shipboard combat rules and a finale variant where it attacks the island itself. Tidal Surge events flood zones on a schedule. The Living Island system makes the skull stir — tremors, zone closures, and a catastrophic awakening if the party pushes too far. The Last Call Tavern expands with Ol' Salty Pete — a barkeep who offers cursed bargains, gambling mini-games, and favors that always cost more than they seem. Six Ghost Crew NPCs haunt the tavern with secrets and routes only the dead remember. New magic items include the Drowned Captain's Compass, the Tide-Turner's Hourglass, and the Eclipse Crown. Five Bloodline Backgrounds and three pirate subclasses — Path of the Blood Tide, the Drowned Patron, and School of Tempests — plus a full Daggerheart conversion appendix. For groups who want to go deeper — a secret Deeper Vault beneath the Pineal Vault, accessible only through dark choices, containing the Lich Admiral's phylactery and a CR 13 boss who fights to test, not to kill. Beyond that, the Admiral's Return — a CR 22 true final boss for tables that want to see how far the rabbit hole goes. Epilogue adventure seeds and a Cursed Survivors mini-campaign extend the story past the island's final dawn. A DM Control Panel with module selectors, play-style configurations, and a one-page tracking sheet ensures you never add more than your table can handle. The island has more secrets than one crew can find. That's why it keeps surfacing.