The nooM

The nooM is an event that only occurs when the player defeats 500 nighttime enemies.
It makes the moon go backwards until sunset. During this time, enemy's sprites and stats are flipped backwards. The stats are doubled before they are flipped. At the end, the player will face huge waves of bosses. However, these ones have only 1 HP.
Completing the event lets the player fight the Cameo Trio.