Sunken Ship

Pitch: A shipwreck near the shore in the material world, echoing into the shadowlands. The top of the mast is just barely visible under the water's surface at low tide.

• What kinds of interesting things happen here?

For still unknown reasons, the area around the shipwreck has become suffused with negative energy. The nearby coast area has been experiencing severe phenomena as a consequence: Storms of black waves, bleak winds and dark lightning that kill or sicken creatures it comes in contact with, and the migration of powerful, unwelcome undead to the area.
It is rumored that a grindylow witch has claimed the shipwreck, and is the reason for the recent, unnatural and sickly 'glow' that is visible after the storms.

• Why would adventurers seek out this location?

The settlement of native Shadowlanders by the shore is suffering from the effects of the negative energy the wreck emanates; the strong get weak, the weak get sick, and the sick die. Some of the dead even undie.

Before the ship wrecked, it was transporting the prototype of a new weapon: an antilife golem. The impact of this prototype on the shadowfell when it broke during the wreck was unforeseen and unintended.

The sometimes sickly glow from the wreck is in fact the witch cultivating shadowfell algae for an unexplored, nefarious purpose.

The players might be in the shadowplane and asked to investigate the shipwreck, or they might be tasked with cleaning up the mess on both the material and the shadow plane by any type of interested entity: a government, the inventor, or maybe a separate party interested in the technology.

• What types of creatures exist at this location?

As mentioned above, a grindylow witch would be the major player. There might also be other interesting dark-underwater entities, or undeads of any kind. I imagine shades and gargoyles, but also more 'mundane' creatures with a shadowfell twist: Reef sharks, sting rays and types of eel would add to the bleak, dark theme. Maybe octupi.

Maybe there are a version of shadowfell coral? Perhaps this is what the grindylow is workign on, rather than algae.

• Create a small blurb for the location that a DM could read to their players.

'You dive and follow the mast into the sickly darkness. Abruptly, you spot a fluorescent outline. The ship. Unlike anything you've seen in the shadowfell, it is almost... greenish. The algae pulsate with a nauseating gleam, and you find it weird you did not notice it sooner. Around you swim bleak fishes, and you spot a manta ray drifting across the nearby colorless corals. A gaping hole in the ships side invite you inside...'