Well, I'm very late. My apologies; I haven't had any good thoughts for adventures. This is partly because of the format I was trying to use. Therefore, I'm going to use a different one, of my own.
A scream, cut off midway. Then it gets quiet.
If I stay, I might learn more. Or be the next to break the silence.
I settle down by the grate, to listen.
(When passing a sewer grating in a mostly abandoned area, at least one party member hears a scream from it, cut off in the middle.)
How odd. It sounds like there's sand shifting down there.
(If they stay, there is a faint but noticeable sound, as of moving sand, or, if the characters would be unfamiliar with that, salt or sugar. After a few days, if they wait that long or return...)
Is that someone digging? And a crank?
(...they hear the above sounds.)
If I could just see in... There.
What are those things? And is that a body?
(If they look through the grate, they will see several Carcass Fiddlers removing a mummified body from a pit full of salt, while one turns a crank, returning a pendulum axe to its set position. Where it goes from there depends on the players.)