UnderFoul is an AU where the human SOUL traits are replaced with Determination (normal), Foul (lesser), and Strange (mix).

About the AU

Frisk actually died but the monsters aren't free, there is a reason for this, for in this au there are only 3 (known) soul traits, normal human souls: Determination, normal monster souls: Hope, and the other humans: Foul, foul souls cannot be used to break the barrier because the soul trait is not as strong as Determination, only 10% of people have these souls and 2 of those 10% fell underground, in place of bravery was a foul soul so it wasn't able to be used so it was left to float forever underground, foul souls cannot break the barrier but they also cannot be shattered nor absorbed for the reason that it wouldn't do anything to boost the absorber, the new child, Lucy, is a Mix, so it is breakable but it looks like a Foul soul, the trait is yet to be named but for now is called "Strange".


  • Frisk's role is filled by Lucy,the Strange Soul, she used to cary around jars so she could collect bugs, now she uses them for her friends Molla and Chara, she stays merciful through every run no matter what.
  • Flowey isn't evil and acts a more like Fell!Flowey.
  • Toriel is still the kind mother, however when she learns of Lucy's SOUL she goes down to destroy the door, instead of mentioning all the children that died before like she did with Frisk, she will say "i wont let you leave, not like he did".
  • Sans makes sure lucy will never touch Papyrus in the Genocide Route by locking him inside their house, but she can break the window to get in.
  • Papyrus is more scared of lucy in genocide.
  • Undyne is far more aggressive when she sees Lucy's soul, she thinks it is a foul soul.
  • Alphys fights Lucy in the Genocide Route and does not help her with Mettaton in the Pacifist Route.
  • Mettaton is less "gay", he is probably the most kind towards Lucy.
  • Asgore will not harm Lucy, when he sees her soul he stops fighting instantly.
  • Frisk is male.
  • Chara is female, her sarcasm and sass makes it seem like she is genocidal even though she isn't.
  • Molla, originally i named her Edward cause at first i planned on making Molla a boy but i changed that when i tried designing her, Molla is the one in place of bravery which is a Foul soul so she has the items you'd find with bravery.