Raven Feather
'A passing raven chose you to carry this emblem. What manner of ill doth this portent?'
Dropped by
get rid of it
This is a penalty, not a trophy. Holding one drags your luck down, and luck feeds drop chances and a handful of other rolls, so a feather left in a corner of your inventory quietly makes every farm you run slightly worse.
The Void Bag counts as carried too, which catches people out, since anything the bag swallows while you are full is still working against you. Extra copies do not deepen the penalty, so one is as bad as ten. The fix is the same either way. Sell them or bin them and do not treat them as collectibles.