Undertale is the story of a human child who falls into the underground, which has become the home and prison of the monster race ever since humans drove them from the surface. Monsters have set up a life in this new place, but long to return to the surface.
I have never played the game, so I had to think about what would be a good idea for the pictures.
It seemed logical to pick pictures of caves, and I was amazed to find out how many great pictures there were of caves all around the world. Because of the nature of the game I tried to only show pictures where the caves were totally underground and no light from the surface could be seen.