Undertale Headcanons

The Gang's location

Nightmare and his gang have no real defined place their main base of operations is, but the place itself is referred to as "Nightmare's Mansion" by a lot of writers. I think their location is in Dreamtale, somewhere among the equivalent of the Snowdin forest. This area makes since because:

1) Nightmare would probably know the area well enough to have the Mansion built privately in a place most people wouldn't just stumble on

2) If Dream were to show up, he wouldn't be able to since Nightmare's presence among the heavy layer of negativity that already surrounds the place after the death of the twin's mom

3) Both twins would like to avoid the place due to past trama, so Dream would refuse to go their unless he ABSOLUTELY had to