In the deeper areas of the Labs we’re going to the Prototype’s actual home.

The place is similar to the home sweet home, it’s a large manor like structure, the decor is similar only more disoriented and ravaged looking with poppy gel on some of the walls, most of the rooms are rather surreal with a lot of them having been warped into bizzare structures filled with puzzles and obstacles, rooms that don’t make any sense, hallways that seem to go on forever, most of this will just be effects of the red smoke that’s in some of the rooms, among other things it’ll make you see now and then…, fake windows like in the Game Station and the Playcare, and maybe portraits with Elliot, Poppy and Oliver’s human selves that have been scratched out by the Prototype’s claws, the whole atmosphere is just nightmarish.

The inhabitants? All the scientists that were converted into toys by the Prototype after the hour of joy like we’ve seen in the chapter 5 arg, they’re really decorations more than anything as depraved as that might be. As for the enemies, well of course the Prototype himself, the wrongside outimals, and pretty much all of the old ones, Huggy, Kissy, Mommy, Catnap, Doey, Lily and maybe others have been brought back as horrid zombified "wrongside out" versions of themselves mixed with the poppy gel, by the Prototype using the parts he didn’t assimilate into himself.

Lore: The place used to be a makeshift home for Poppy and the Prototype that they were originally kept in, it was made by Elliot Ludwig before his passing, after his passing they were taken and put in the more traditional holding cells in the upper labs that all the other experiments were kept in, leaving this place pretty much abandoned as a result until the Prototype made it his lair.

This could make for a very iconic FNAF 4/psychological horror type experience to fit with this apparently being the finale of the series.

Chapter 6 Location Prediction.