Spell of Oblivion

Spell of Oblivion (망각의 주술, Mang-gag-ui jusul) is a spell that used to erase many people's memories all at once.

Po Bidau Gustang used this spell to erase the memory of all 43rd Floor citizenz. While the Disciple of Workshop used this spell to protect the Hidden Floor, so those who have stored data of themselves in the mirror reveal anything about that place to the outside world, they will forget about the existence.