Trickery

Rotten Bones did not have a base in Wickidor, but had the overwhelming advantage of numbers compared to Leah's party of six, especially after their coadjutor arrived as reinforcement.

Having received a sign from the evil god called Rotten Bones, they immediately went up in force and set up ambush points by every gate in Wickidor. 

Leah, who never expected that her value to Rotten Bones had suddenly become so important, was planning to lead her guards out of Wickidor from an alley in the east when they all ran headlong into cultists who each had a black corpsefly with them.

Although the guardsmen managed to unleash their might and repel the cultists thanks to their Systems, they never caught on that the cultists were just buying time. The moment they had caught sight of Leah, they released their black corpsefly which led the coadjutor of Rotten Bones to them!