(Not to be confused with the regular Dungeon)
A "Mind Dungeon" is a form of Dungeon on the Heroic Path.
They're unique in that you enter a persons mind in order to save them and they have unique enemies.
At the moment, there's three Mind Dungeons.
Valerie's Mind, which is basically a roller skating rink with sentinent roller skates.
Sarah's Mind, which is as if the entire world is on fire. Including the enemies.
Julia's Mind, which is a library. This comes as a surprise to exactly no one who knows of her.