The Church of the Howling Autumn

The first One Page Dungeon adventure of "The Cycle of the Four Churches"  I am writing. In this one, PCs will explore the Church of the Howling Autumn: a desolate place where it is said ancient secrets are hidden, a distant place that many tried to find, a place from where, of course, no one as ever returned... Which treasures have been buried in the Church? What is the distant howling people hear from the bottom of the mountain? Who uses the bells? 

Will you be able to find your answers?