Undermyth is an alternate universe created by reddit user sp441, also known as 441.
It is a role swap AU that puts an emphasis on keeping character personalities and how that would affect their surroundings.
- In the RUINS, a new town can be found by the name of New Old Home.
- A new flower also by the name of Flowey takes the position of canon Flowey. The new flower helps Frisk along their journey.
- Many NPCs originally seen in the ruins can be found in New Old Home.
- The ghost in the Dummy is now a gentlemanly ghost, known as Pladstabloke, who herds snails.
- The rock set up a toll booth in front of the town and she demands smiles to pass.
- The spiders now run a shop selling various pastries.
- The random encounter enemies in the RUINS now live in New Old Home.
- Asriel is now the king of the RUINS, and he tries to stop Frisk from progressing.
- The cut enemy Doge (pronounced dohj) is now captain of the royal guard, appearing in snowdin. Her full title is Captain Bassiere Von Dohj the Third.
- Papyrus serves under Dohj in the guard as a private investigator.
- Monster Kid works as his apprentice.