Fast-forward to the present day, and you find yourself in the shoes of a human child who has fallen into the Underground. You soon discover that the Underground is divided into several regions, each with its own ruler. There's Snowdin, the frozen tundra, ruled by the lovable but intimidating Sans; Waterfall, a mystical realm controlled by the enigmatic Undyne; and Hotland, a volcanic region, where the fiercely protective Mettaton resides.