If someone handed me a treasure map tattooed on a nicely-tanned piece of human skin, I'd probably scream and run away! Hopefully your party is made of sterner stuff, for this is a map made by the legendary pirate Bloody Jack Dascombe, proportedly giving the location of his ill-gotten gains, including loot from an Imperial treasure fleet that he plundered an hundred years ago.
The background is simple and straightforward, telling of a brutal pirate, his infamous last raid, and the 'Empire' whose treasure fleet he robbed... and his ultimate fate, like most pirates, at the end of a rope. References are loose enough for you to weave this all into your campaign world's history, possibly enriching it in the process. The map does show the way to the treasure, it just omits to mention minor details like the traps and other threats a would-be robber will face. There's a few ideas for how you might get the party to the right place, as the action presented here opens with them on the right island to commence their explorations. The island is uninhabited, but previous residents have left traces behind. With these and more will the party have to contend.
Then you find out what's really there, and who created the map and why. These are all matters to keep very quiet about until the party is committed to this adventure. Suffice to say that the labyrinth is being actively managed, and that it's largely filled with undead and other recruits from Hell. This is no walk in the park. There again, the treasure is pretty magnificent if the party ever reaches it. (Of course they then have to figure out a way to get it home unmolested...).
The adventure itself comes in five 'levels', the first being the island itself. It's well described with sufficient clues that the party ought to realise that it's not quite right. The second level is the complex left by former inhabitants. Sea tunnels and no less that TWO labyrinths make up the rest, providing ample scope for delving - including the possibility of underwater combat. Throughout, there are detailed atmospheric descriptions coupled with monster information, combat notes and stat blocks.
This adventure offers a hard-fought slog to get to a treasure that is going to be difficult to actually profit from acquiring, not to mention a couple of little twists at the end that might spoil the party's enjoyment of their new-found wealth. The entire piece is written in a 'GM/Designer-vs-Players' style, combatative rather cooperative story-telling (although of course you can run it however you like). It provides a nice challenge for a mid-to-high-level party, something that can often be quite hard to balance. And the idea of a 'managed dungeon' is really rather neat and hangs together well.