Delta Rune is a role-playing video game created by Toby Fox, the developer behind the popular game Undertale. Released in chapters, it features a mix of exploration, puzzle-solving, and turn-based combat. Players control a character named Kris as they navigate a mysterious underground world filled with unique characters and challenges. The game is set in a universe that shares some elements with Undertale, but it introduces new themes and gameplay mechanics. Players interact with various characters, including Ralsei and Susie, while uncovering the story and making choices that affect the game's outcome.