From Introduction:

This encounter is designed to introduce the characters to a beholder cult. It does not pit them directly against a beholder, although it can be adjusted to do so if the GM wishes. Instead, it puts them in conflict with the cultists who serve the Dominion of the Poisoned Eye.

The encounter can take place in a city, but it works best if the abbey is the only accommodation in miles, probably in a hamlet or along an isolated road. The monks of a monastery have set up an inn to feed travelers in the area. They charge 5 sp per night, which includes lodging, dinner, and breakfast.

The inn is separated from the abbey by a thick wooden door. The monks prepare and serve the meals. They are dressed in thick woolen cloaks, but most keep their hoods down inside the inn. They have shaven heads and a variety of racial backgrounds. The food is simple, but hot and filling. Ale and wine are also available, although each mug or glass is 5 cp extra. The sleeping rooms are on the second floor above the common dining room, which is separated from the abbey by a thick wooden door.

The Cultist-Monks of the Abbey Inn is a free encounter that introduces characters to the eyekin, beholder cultists, and vast conspiracies ruled by the eye tyrants found in The Complete Guide to Beholders.