Rotten Penny
TrinketAfterbirth+Locked
How do you unlock Rotten Penny?
In The Binding of Isaac, Rotten Penny is unlocked by unlocking Rotten Penny (Achievement).
Structured pathSource-backed requirements are mapped into trackable steps.
Spawns a Blue Fly every time a coin is picked up.
How to unlock: Have 20 Blue Flies at the same time
What unlocking Rotten Penny leads to
Nothing depends on this yet.
Source: bindingofisaacrebirth.wiki.gg
Imported 2026-09-13