A group of ghosts is haunting the church
The church in town is experiencing a haunting. Parishioners are being frightened away. The priest will pay 80 gp to any party who can rid the church of the ghosts.
When investigating, the party will discover a green ooze on the bookshelves of the priest’s office. When they investigate further, a green ooze (use the grey ooze) will attack them.
Inside a closet, they’ll find a gelatinous cube.
Eventually, a ghost (or 2 ghosts, if the party is Tier 2) will appear floating in the narthex of the church.