Deltarune is an indie role-playing game by Toby Fox, released in chapters beginning in 2018 as a follow-up to Undertale. Dark fountains are central to its story, opening the shadowy Dark Worlds that Kris, Susie, and Ralsei explore. The fountain sound has become a recognisable cue for fans, shared in gameplay clips, edits, and theory videos across YouTube and TikTok. Its slow, ominous build makes it useful beyond the game itself, and it remains popular because it instantly signals mystery, transformation, and a world about to change.