Brimstone's shop is a portal from Eretz to Earth. Human hunters go there to trade Brimstone teeth for wishes, but many traders avoid the shop because when you enter, you have to wear one of Issa's snakes around your neck. Some people try to avoid this ordeal at all costs.
Karou grew up in the shop since she was a little girl. She grew up learning about teeth and running errands for Brimstone.