The party spots a pair of githyanki ships in the distance, with a silver albatross on a black flag as their banner. A whispering wind sent by the pirates tells the PCs that they're approaching the waters of the Derelict Sea, a huge swath filled with ruined and abandoned ships. The githyanki control this territory, and they offer to show the PCs the safe route through if the PCs hand over all wealth they possess, including their magic items.
If the PCs balk, the githyanki warn them that they'll never make it through on their own. If they fight, well, you've got your combat, and you can toss in a roleplaying scene where a surviving pirate offers to guide the PCs through if they spare his life and let him keep one of the ships as his own.
(On the off chance the PCs take the githyanki up on their offer, um, have them sail to a pirate's cove, where the commodore of the fleet gives them another choice. She can place a geas upon them, tasking them to retrieve some item [which conveniently is located where they're headed anyway], and bring it back within X time period. You can use this as an opportunity to add a minor quest in, and you establish the pirates as recurring characters who aren't necessarily villains.)
Still, I figure the party will decide to set out their own way and try to heroically cross the Derelict Sea. They might try to sail around it, but even if they could guess the borders of the region, we're talking planar distances here. Hundreds of days at sea, and I assume they have some time limit.
So, they sail through the sea. Occasionally they come across floating wrecks of ships that must have drifted here for centuries. No sign of the crews. No real treasure either (though feel free to drop a map here, or some clue to a future plot thread you might want to involve).
On the third morning (is there day and night in this place?) of the ten day trip, as they cut through fog-shrouded, still waters, the ship runs across a sandbar, which actually is the sunken corpse of the dead god of putrescence and spoilage. After the requisite "horrific undead beings clamber out of the sea and attempt to kill everyone while the party struggles to free the ship and sail on," the PCs discover that all the food on the ship is ruined.
The PCs need to make Endurance checks to go without food, and when they finally do get out of the Derelict Sea a week later, they spot a pod of whales. All the food they could need, and all they have to do is succeed in a hunt against psionic cetaceans.
I'll be back!
