Towers of Night (5e)

From the introduction:

This is an adventure for four to five 1st-level player characters...Ages ago, long before the Lord of Sloth took control of Zeland, the people of the nation were interred within great Towers of Waiting when they passed. The bodies were carried to the roofs of massive stone towers, where they lay in rest for a year's time. Here elements battered the body, removing the flesh and sending the spirits onto their next destination. After a year passed, the sun bleached bones would be cast down into the base of the tower, where a massive pit waited. This was the way of the first Zelanders, for the first 500 years. The Battleplain, where this adventure takes place, is a region dotted with many Towers of
Waiting.