Unlike Tartarus and the Midnight Channel, Palaces, in Persona 5/Royal, are distortions created by the negative and/or corrupt emotions of a Palace Ruler. Each Palace has a Treasure, which is essentially the catalyst of said Palace in physical form. Stealing this treasure causes the Palace Ruler to have a "change of heart," and the Palace itself to collapse. Persona 3 Reload does not have "Palaces," but rather Tartarus.