The Machine Key open The Machine dungeon.
The Machine is a medium-level dungeon introduced on April 1, 2019 for April Fool’s Day. The dungeon is dropped by The Glitch (an enemy which only appears for April Fool’s events) at a guaranteed rate. Outside of events, this dungeon also drops from Steel Contructs at a very low rate. The dungeon consists of a single boss fight against Null, with the only other enemies in the dungeon being the boss’ minions, called The Servers.
Despite being an April Fool’s dungeon, it is recommended to be prepared before entering The Machine. The boss is very powerful, and both it and its minions are capable of dealing serious damage.
It is a source of a number of April Fool’s items – although unlike some other items of their kind, these joke items are not completely useless.
Under certain circumstances, Null can drop a portal to The Inner Workings.