Impossible Mode is one of the challenges in Custom Night, with all the characters set to 20, the highest AI.
Due to it being set to the highest AI, it is the hardest mode to manage out of all the Custom Nights, however, if you are experienced with the game enough, you can beat this mode no problem.
Trivia
- When you beat Impossible Mode, you'll unlock the rest of the challenges, the cheats, and Strings in the Character Profiles Section of the Extras.
- Upon completing Impossible Mode, you will be treated with a 8-bit Cutscene, describing both Fritz Glade and Purple Guy growing up, following some of the events of FNaF 3. The cutscene ends with Fritz Glade taking the Springtrap Mask, and went on to make Popgoes the Weasel and/or Weasel