Deltarune is a later role-playing game from Toby Fox, the creator of Undertale, a series known for letting players choose mercy or violence and for making those choices matter. Fans borrowed the term genocide route from Undertale to describe the darkest way through Deltarune, and short clips of its ominous cues spread through YouTube edits, streams and soundboards. They remain popular because they instantly signal a moral turning point, letting creators borrow the game's unsettling atmosphere without using a long scene or spoken dialogue.