Frankensteinway is a new boss added in the Amplified DLC. He is fought in Zone 5 when playing as Nocturna.
During the battle, Frankensteinway has 4 phases, each with 10 health. The boss room has 4 electricity generators with buttons next to them that will deactivate them (alternatively can be destroyed by bombs). Unlike most enemies, Frankensteinway is 2x2 tiles large.
In the first phase, Frankensteinway will stay idle for several beats, then move 3 tiles in a random direction. When he begins to move, random patterns of tiles will flash with electricity, which will damage the player if they step on those tiles. During this phase, 2 white sarcophagi will spawn at the top corners of the room.
In the second phase, one of the four generators will turn on, and Frankensteinway will become invincible until it is turned off. The 2 white sarcophagi will respawn if they were killed in the last phase. Otherwise this is the same as phase 1.
In the third phase, Frankensteinway behaves the same as the second phase, but he will no longer summon electricity in patterns when he moves. Instead, waves of damaging electricity will constantly move down from the top of the room, similar to the Golden Lute's fire attack. Also, the sarcophagi will respawn again and turn yellow.
In the fourth and final phase, Frankensteinway will charge across the room cardinally OR diagonally after several beats, similar to Dead Ringer, breaking anything in his path (including the generators). Meanwhile, The sarcophagi will turn black, and the waves of electricity will continue to spawn.