Susie chooses not to help, only wanting to return to her own world. Before she can leave however, the three encounter Lancer, the King's son, who tries to stop them from proceeding with various poorly thought out plans. Susie eventually decides to join Lancer, leaving Kris and Ralsei on their own. As Kris and Ralsei make their way to the King's castle, Susie befriends Lancer, and the four ultimately become a team. Upon realizing that they will have to confront the King, Lancer runs off to the castle and arranges for the King's henchmen to throw Kris, Ralsei, and Susie into the dungeon.
Susie escapes the dungeon and confronts Lancer, who explains he wanted to keep Susie and the King from hurting each other. Susie promises Lancer she won't hurt the King. Kris, Susie and Ralsei go to the top of the castle and confront the King in battle. Eventually, the King falls to the ground in exhaustion and Ralsei takes pity on him, healing the King. However, this is revealed to be a ruse as the King quickly incapacitates the three heroes, threatening to kill them all. If the player has resolved enemy encounters without violence throughout the game, Lancer turns the King's men against him and imprisons him, taking his father's place. Otherwise, Susie subdues the King using Ralsei's Pacify spell.
Kris closes the Dark Fountain, so that they can return to their own world. There, Susie says goodbye, expressing interest in returning to the Dark World. The player can explore the town before having Kris go home to bed. That night, Kris shakes in bed, then falls on the floor and limps to the center of the room. Kris tears into their chest and rips out their heart-shaped SOUL, throwing it into a birdcage in the corner of the room. The player can move the SOUL around the birdcage, but cannot do anything else. Kris draws a knife and turns toward the viewer. They smile, with their right eye flashing red.
Gameplay
Like Undertale, Deltarune is a role-playing game with a top-down perspective. The player directly controls a human named Kris, but they may also choose attacks of other characters in the game. Similarly to Undertale, Deltarune includes puzzles and bullet hell sections in which the player must move a heart around a boxed area while avoiding attacks. Undertale's random encounter system has been removed; players can now see the enemies directly on the field, allowing for the possibility of avoiding them.
Combat is turn-based. Players can choose from a set of actions each turn such as fight, act, spare, using an item or defend, which reduces incoming damage. Brushing against attacks without touching them increases the Tension Points (TP) gauge, which allow party members to use spells. For example, Ralsei can pacify enemies by singing them to sleep. When a party member's hit points (HP) reaches 0, they become downed and can't fight anymore. The HP of downed party members will regenerate automatically until it reaches 1; healing items or Ralsei's healing spell will also revive them.
While the goal of the game is implicitly to avoid fights and spare monsters, this is made difficult in that Susie—who is not initially controlled by the player—would attack enemies rather than spare them, and thus the player must also warn enemies of Susie's attacks if they want to show mercy.
Development and release
The idea for Deltarune came to Toby Fox in a dream he had in 2011 while he was at college. In the dream, he saw the ending to a video game, and was determined to create it. Fox was also inspired by a collection of playing card designs posted on Tumblr by artist Kanotynes, which were used in the final game. Development of the game started in 2012, although it was abandoned before Fox created the first room. Some music from the original project was recycled for Undertale, most notably the main battle theme (which became Papyrus' battle theme), and a song called Joker Battle (which was reused for the Toriel fight). After the Kickstarter success of Undertale, Fox decided to make a game combining the two. Various factors such as the graphics, overhauled combat system and Fox's mental state make Deltarune a more challenging game to produce compared to Undertale.
Fox came up with Susie's design after having played Phoenix Wright: Ace Attorney. He originally based her off Maya Fey and she would act "nice and cute". However, as her design progressed, she eventually turned into more of a "thug". Fox stated that he planned to give an unnamed character a fire spell which they wouldn't be good at using, but decided against adding it in the first chapter. Temmie Chang served as the main artist for the game, designing characters, sprites and animations. Chang previously assisted Fox with character art in Undertale.
