Dess Holiday is a yet unseen character in Deltarune. She is a daughter of Rudolph Holiday and Mayor Holiday, and older sister of Noelle Holiday. Dialogue by Noelle in Chapter 2 heavily implies that she is either deceased or missing.
Very little is known for certain about Dess, but according to Noelle's recollections she was very protective of her sister growing up, often comforting her in terrifying situations or defending her from Kris's antics.
What a strange moon...
It's like nothing I've ever seen before.
... I wish Dess could see this.
According to Noelle, Dess used to be in the same friend group as her, Asriel, and Kris, and on one occasion they all hung out in the forest by the graveyard together. Dess is also responsible for Noelle's love of horror movies, as they remind her of their time together as sisters. Despite the Holiday siblings' described close relationship, Dess is conspicuously absent from Hometown with no mention of her being present in the family's life anymore, suggesting something happened to her before the events of Deltarune.
Dess is first alluded to by name through an object that can be inspected in Rudy's hospital room: an angel doll that Rudy explains was made by Dess and Noelle in youth group. He keeps it as a good luck charm.
If Kris tells Noelle that Susie "eats chalk" when they meet her outside her house, she at first thinks Kris is joking like the time they told her that ICE-E was real and ate kids. She recalls Dess smacked Kris with a wiffle bat until they stopped lying.
If Kris, intentionally or not, repeatedly scares Noelle by causing mice in Cyber City to collide with her, she remarks that Kris is lucky that Dess isn't there to protect her.
While exploring the city, Noelle and Kris come across a path that is intermittently blocked off by forcefields that can be disabled by each of them stepping on a panel. As they travel, Noelle recalls the time she spent with Dess, including an incident where she, Kris, and Asriel hung out in the forest by the graveyard. Dess comforted Noelle, who was terrified.
Noelle looks up at the moon in Cyber World's sky and remarks that she wishes she could show it to Dess. Later, while riding the Ferris wheel with Susie, Noelle remembers watching horror movies when she was little with Dess.
If Kris inspects the angel doll in Rudy's hospital room, Susie starts to tease Rudy for keeping it, until she hears that Noelle made it with her sister. Susie is visibly perturbed at the mention of Dess and opts to not say anything more.
- It is implied that "Dess" stands for "December," keeping with the Christmas theme of the Holiday family. The strongest evidence for this is during the sequence where Noelle recalls spending time with Dess, Kris, and Asriel in the graveyard: the letters on the steps she is stepping on spell out "DECEMBER."
- Noelle froze on the word "December" during a spelling contest from Berdly's flashback.
- Noelle's room in Queen's Mansion has a calendar where every day is December 25.
- Since her room is based on her internet search history, this implies she is searching for "December Holiday," her sister's full name.
- The way Dess is described in Chapter 2, as well as comments regarding the Holiday family throughout the game heavily implies she died or went missing sometime before the events of Deltarune:
- In Chapter 1, Noelle is unable to go home when she forgets her key because no one is there to let her in.
- Rudy claims that without him, Noelle doesn't have someone to protect her from her mother's strict behavior.
- Susie immediately stops teasing the angel doll upon hearing Noelle made it with her sister, and is visibly perturbed at the specific mention of her sister. This suggests Susie knows about some circumstances regarding Dess.
- Although they never make a physical appearance, Noelle and Dess are known to exist in the Undertale universe alongside their father. In the unused Undertale alarm clock dialogue, Asgore remarks that Rudy's daughters both get to grow up in the sunlight. In the Xbox version of the Dog Shrine in Undertale, Sans mentions "the antlered girl and her big sis," with the latter most likely referring to Dess.
- The way that Sans phrases his reference to "the antlered girl" may imply that her sister, in contrast, does not have antlers.