That Old Machine

The machine in the Skeleton's basement. There's lots of speculation on what it is used for. Is it a portal to different aus? Different timelines? Is it a machine to trap the Player? Is it a machine to free Gaster? Or is it something much, much simpler? Something... forgotten? Memories of a history lost in time?

Prequel: What it Means to Persevere
Sequel: Lost and Found