From publisher blurb:
In Monstrous Electric Eel, a level-6 Shadowdark RPG one-shot, the adventurers come to the city of sirens, Caliphaia. The heroes answer their call for help or come to their aid after learning of a gigantic monster that attacked their city. Their beloved Pearl of Life was stolen in the process.
The characters meet the sirens but must leave soon. The monster escaped by using a black hole and the heroes must follow. The other side of the portal takes to merfolk territory. Sirens do not know how it happened, but the monster obeys the merfolk's orders and commands.
TThis is an underwater adventure that brings the heroes to the beautiful city of Caliphaia. They must gather information and leave soon to track the beast. They must defeat the monster and retrieve the Pearl of Life.