The Binding of Isaac: Rebirth
637 Achievements
800-800h
Steam
Rotten Penny
Unlocked a new item.
38.4%
How to unlock the Rotten Penny achievement in The Binding of Isaac: Rebirth - Definitive Guide
redjarman
TrueSteamAchievements
TrueSteamAchievements
This is unlocked by having 20 blue flies at once.
There are many ways of spawning blue flies in the game, but the easiest way to ensure you have them all at the same time is to use the Jar of Flies item. For every kill you get, a fly is added to the jar, once there are 20 inside, just use it to release them all at once.
There are many ways of spawning blue flies in the game, but the easiest way to ensure you have them all at the same time is to use the Jar of Flies item. For every kill you get, a fly is added to the jar, once there are 20 inside, just use it to release them all at once.
