Al Niente, also known as "The Apocalypse," is an apocalypse-like state the world seems to have plunged into for unknown reasons before the game's story begins, around 250 years ago. It still spreads now. Affected area will gradually lose color and sound in the beginning, then everything will eventually freeze in a desolation as if the world has stopped turning.
It's a weathering force that stops all sound and creation, eventually plunging the world into desolation. When Al Niente hits Notalium, the Notalium turns into a corrupted and disordered state. Fisica and Ritmo, are tasked by the Notalium Administration to travel the world to purify it from Al Niente artificially. To do this they are equipped with a device known as the Notalium Tuner, a device made by Fisica capable of turning disordered Notalium back to its ordered state through a process known as "tuning". Through this process, the ordered Notalium can be used to traverse through disordered Notalium, but only for a short amount of time before Al Niente can take back control.
It is unknown how long it takes for the ordered Notalium to become corrupted.
Al Niente can have an effect on humans as well, though what these effects actually are is still unknown. With ordered Notalium close by (such as Ritmo's pendant or Rossa's earrings), they are immune to the effects.
Al Niente means "to nothing" in Italian.