This module follows the events of Module M4: Part-Time Professional Mine Janitors, in which the mouse adventurers recovered the Stellar Keystone—an object of immense arcane potential nearly lost to an unknown enemy. Though the relic has been returned to the human world, the identity of the figure who ordered its theft remains a mystery.

The party begins this adventure with a new lead: a Grey Mist contact in the wetlands claims to know who orchestrated the heist. All signs point north, toward the edge of Portal Lake, where strange omens stir among the reeds—abandoned shrines, nervous locals, and whispers of new powers rising.

Kurtulmak, a cat demon whose influence is growing among the rats and voles, has sent her chosen servant to seize another object of power: the Golden Egg, sacred vessel of the Great Duck. If corrupted, it may serve as a substitute for the Stellar Keystone, allowing Kurtulmak’s influence to deepen and spread. Her high priest Nasuriel, a blue heron of terrible power and ambition, now seeks to defile the Egg and ascend to even greater power.

The players’ first task is simple: meet their contact. But as they travel deeper into the marsh, they will uncover the true stakes—and be drawn into a widening conflict that threatens the balance of life around Portal Lake.

This adventure is designed with flexibility in mind, offering numerous opportunities for Referees to scale challenges and modify encounters to suit their group’s needs. Its modular structure and detailed descriptions ensure that both novice and experienced Referees can adapt the material with ease, crafting a game experience as whimsical, perilous, or dramatic as their table demands.