While there was no indication for it, the entire cave belonged to the goblin king and by entering inside any adventurer became his property to do whatever he wanted with. (Doomsatan666/ Isatan)
LF Color Source: "Kazuma!!! There is a spider in the bathroom!" 1girl, aqua (konosuba), arm up, blue eyes, blue hair, blush, hair between eyes, hair ring, long hair, open mouth, pointing, sidelocks