From publisher blurb:
Cultist Monastery is a Fifth Edition plug-in adventure for four characters with an average party level (APL) of 3, 5, 8, or 11. This addon offers a general guideline on scaling the adventure for each level, and includes a table with adventure hooks for you to adapt to your own campaign. The characters must either aid, infiltrate, or defeat the Cult of Yil in their monastic home to claim the angry god’s Extinction Arch, an artifact capable of penetrating the underworld.
You may also run this adventure as part of the Dungeon & Lairs Megamodule #2: Seekers of Yil. If you do, refer to the Seekers of Yil megamodule’s adventure hook, “The God of Secrets Appears,” to get your characters involved in the story. Learn more about the Seekers of Yil mega module on DMDave’s Patreon.