The Underwhere, also referred to as World -1 in reference to the Minus World glitch in the original Super Mario Bros, is a location in Super Paper Mario. You arrive there first by Dimentio who kills Mario, (or getting a game over but you don't unlock 7-1) and Mario ends up there. It is quite a desolate landscape. Once you arrive there, you see Luvbi, the daughter of Queen Jaydes, who insults you in an incomprehensible manner. As you progress through The Underwhere you'll see many people including Luigi, Shaydes, and D-Men. After meeting Queen Jaydes, and rescuing Luigi, you will be able to return to Flipside. However, your time there is not over. You will have to return as the Underwhere is the starting point of chapter 7. In 7-2, you will progress through the underwhere road to bring Luvbi back to the overthere to see her father, Grambi.