|Bandit Hideout exit|
The Rusted Key is a 1-time-use key dropped by only bandits and Bera the Blade that open an exit to the overworld in the Bandit Hideout. This is located in Bera the Blade's section, which is at the bottom left of the Bandit Hideout.
During 0.3.3, the Rusted Key was used to open the old Bandit Hideout. The key used to drop from any mob and had a one-time-use to get into the hideout. However, the sewers were redesigned and this feature was removed.