This option creates a Scarescraper with infinite floors as well as its own difficulty, also named "Endless".

Unlockable	How to unlock
Hunter Endless	Beat a Hunter mode in a 25F Scarescraper, then "Create a Scarescraper".
Polterpup Endless	Beat a Polterpup mode in a 25F Scarescraper, then "Create a Scarescraper".
Rush Endless	Beat a Rush mode in a 25F Scarescraper, then "Create a Scarescraper".
Surprise Endless	Beat a Surprise mode in a 25F Scarescraper, then "Create a Scarescraper".