"Doesn't it upset you that you're reality's drug? As soon as you're introduced to a universe, everything starts to depend on you..."

"Une Folie Partagée Par Le Monde Souterrain" (A Madness Shared By The Underworld) is an AU for Undertale created by User:Aidanthehedgehogisawesome.


Une Folie Partagée Par Le Monde Souterrain is a role-playing game that utilizes many of the traditional mechanics normally seen in role-playing games but with a number of differences.

The battle system in Une Folie Partagée Par Le Monde Souterrain is turn-based and seems to be heavily inspired by bullet-hell games - in particular, the Touhou series - where the protagonist's SOUL, represented by a red heart, must avoid attacks unleashed by the opponent. As the game progresses, new elements are introduced, such as colored obstacles which require the soul to stand still or move through them, and boss battles which change the way the heart is controlled.

However, a clever element is that each different 'route' the player can take introduces differing personalities by the characters. (i.e. on a Genocide Route, Toriel becomes the hesitance, Sans becomes the rage, Papyrus becoming the hope you can still get a good ending)

Une Folie Partagée Par Le Monde Souterrain's character's personalities, in a more complex standard, is, with each action taken (movement patterns, routes, interactions) the other characters are slowly - and directly - reshaped to fit somewhat into that of the player.


The characters are that of Undertale's, though with obvious differences, however.

Each character can be reshaped; such as Toriel becoming patience in the Pacifist Route.


  • It was, actually, inspired by 20 Dollar Nose Bleed by Fall Out Boy ft. Brendon Urie.
  • Sadly, the title cannot be translated correctly. The Google Translate version makes it "A Folly Shared Through The Underworld", and it's original translation is "A Madness Shared By The Underground".