Closet Dark World
The closet Dark World[note 1] is the first Dark World that Kris and Susie encounter in Deltarune.
The closet Dark World is located in the school's supply closet and consists of two areas: an unnamed cliffs area and Castle Town, the latter of which houses Ralsei's castle and the Grand Fountain.
At an unknown time, a Dark Fountain of "pure darkness" – known as the "Grand Fountain" – was apparently created in the school's supply closet, giving form to a Dark World.
The true age of the closet Dark World is unknown. The legend of DELTA RUNE implies the Fountain has stood tall for "millenia",[sic] allowing "LIGHT and DARK [to live] in balance".
For an unspecified period of time, Ralsei was the only inhabitant of this Dark World, until the Great Door to Card Kingdom was opened, allowing Lancer to enter, followed by Kris and Susie entering the closet at the beginning of Chapter 1.
When Kris and Susie are sent by Alphys to retrieve chalk from the supply closet, they discover a supernatural darkness within the room, unnerving them. Going inside, Kris and Susie find the closet's interior much bigger than expected. Unable to find the chalk, Kris and Susie turn to leave only for the door to slam in their face. Suddenly, the floor gives way, and Kris and Susie enter free-fall, disappearing into the darkness.
Some time later, Kris awakens in an unknown area and reunites with Susie. After evading the attacks of a shadowed figure, the pair slides down a cliff-face and escapes to Castle Town. There, Kris and Susie meet Ralsei, who attempts to inform them of the legend and the emergence of the Eastern Fountain. Ralsei shares his belief that they are the Delta Warriors of the legend; however, Lancer, the shadowed figure from before, interrupts him and attacks.
Following the scuffle with Lancer, Susie splits off from the group and heads east. Kris and Ralsei follow suit, traveling through the Great Door to reach the Field, moving from the closet Dark World to Card Kingdom in the process. Later, after sealing the Eastern Fountain and returning to the Light World, Kris and Susie find themselves in the unused classroom, to the east of the closet and the closet Dark World.
Thrilled by their adventure, Susie asks Kris to return to the closet Dark World the next day.
Upon re-entering the closet the next day, Kris and Susie are transported directly to Castle Town. The party cannot climb back up the cliff on the western edge of town, making the cliffs area inaccessible. Ralsei greets the two, and Susie notices Lancer and other Darkners are absent. Ralsei asks her to wait before whispering to Kris to return to the Light World and bring all the items from the unused classroom to Castle Town.
Once Kris returns with the items, the Card Kingdom Darkners appear in Castle Town, and the town square transforms.
As Kris nears the entrance, Susie expresses disinterest in doing the group project. Ralsei overhears, and "banishes" the two until they start their project. Lancer, Rouxls Kaard, and, if found in Chapter 1, Starwalker, join by becoming Key Items before Kris and Susie leave.
Following their adventure in the Cyber World, Kris and Susie can freely travel back and forth between Hometown and Castle Town until the player chooses to complete the Chapter. The party can find the Cyber World's denizens in Castle Town if they were recruited.
Kris and Susie can optionally visit the closet Dark World while exploring Hometown in Chapter 4, where they are freely able to leave, SAVE, and re-enter it. Any recruits from Chapter 3 can now be found around Castle Town; Susie also brings Tenna to the closet if he has been repaired and not yet gifted to anybody. Castle Town changes appearance again, and if enough characters were recruited, the new TV Studio building can be entered and the background music changes from My Castle Town to Castle Funk. Other buildings like Ralsei's castle, the Dojo, and the Cafe also differ from Chapter 2.
The closet Dark World is inaccessible after sealing the Dark Sanctuaries, as Susie refuses to enter the school. However, it can be accessed via a Chapter 4 Completion FILE and a SAVE file that has defeated the Sound of Justice. Upon loading the SAVE, a short cutscene plays, where a light similar to that of the closet Dark World's entrance appears next to the Great Door in the 3rd Sanctuary. Backtracking to this point and entering the light transports Kris to the closet Dark World. Only the Cafe and the TV Studio can be accessed. New recruits from Chapter 4 can be placed and talked to in the Cafe, and the code to Mike's room now appears in the TV Studio, allowing Kris to meet the Mike impersonators if the code was not entered earlier. Kris can return to the 3rd Sanctuary by leaving the closet Dark World as normal.

This quiet, dark purple area consists of long, straight roads with dust mounds scattered about, and broken rectangular architecture in the distance. The cliffs occasionally depict eyes and a dark liquid substance. While the majority of the area only appears in Chapter 1, the east-most cliff connects to Castle Town, where Shadow Crystals and equipment from defeated Shadow Crystal bosses from previous Chapters can be found.

Castle Town primarily consists of contorted dark houses with multiple windows, and pitched rooftops. Excluding Ralsei's castle and the Grand Fountain, the area is nearly empty. From Chapter 2 onwards, Kris and Susie land near the front of the town square. The area grows with new buildings as the story progresses, with new Darkner residents arriving from the other Dark Worlds. The amount of Darkners and available effects varies based the route and if they were recruited.
- The short sound that plays upon Kris and Susie landing in the closet Dark World from Chapter 2 and onward is internally referred to as
snd_him_quick,[1] and appears to be a sped-up snippet of the choir from ANOTHER HIM.
- ↑ "closet Dark World" is a conjectural title.
- ↑ gml_Object_obj_dw_transition_Draw_0 script, line 458, Chapter 2