Dreadful Gallery is a creepy world accessible from the dancing frame in Red & Blue Passage.
Features
This world contains walls with odd paintings hung on them, most of which feature body parts. There are mutant NPCs walking around the place as well. There is a creepy white creature with lots of teeth that can be found flying around the place. One of the paintings has a golden frame instead of a brown one. Interacting with it will take you to the Forsaken Cliff.
Directions
Kubotsuki's Nexus → Nail Board → Red & Blue Passage → Dreadful Gallery
Gallery
Entrance to the Forsaken Cliff.