About me: "And finally, I must tell you that this year, the third-floor corridor on the right-hand side is out of bounds to everyone who does not wish to die a very painful death."
-- Albus Dumbledore
Third floor corridor
Also known as the Forbidden Corridor, this is where Fluffy guarded the trapdoor to the hiding place of the Philosopher’s Stone. Students are advised to avoid it if they do not wish to die a painful death, as per Albus Dumbledore’s welcome speech at the beginning of Harry Potter’s first year.
J.K. Rowling inspired by Cerberus the Three headed Dog Guardian of the Underworld in Greek Mythology, recommendations to read The Golden Ass, from Apuleius.
PSYCHE AND THE UNDERWORLD
The last trial Venus imposes on Psyche is a quest to the underworld itself. She is to take a box (pyxis) and obtain in it a dose of the beauty of Proserpina, queen of the underworld. Venus claims her own beauty has faded through tending her ailing son, and she needs this remedy in order to attend the theatre of the gods (theatrum deorum).
Once again despairing of her task, Psyche climbs a tower, planning to throw herself off. The tower, however, suddenly breaks into speech, and advises her to travel to Lacedaemon, Greece, and to seek out the place called Taenarus, where she will find the entrance to the underworld. The tower offers instructions for navigating the underworld:
The airway of Dis is there, and through the yawning gates the pathless route is revealed. Once you cross the threshold, you are committed to the unswerving course that takes you to the very Regia of Orcus. But you shouldn’t go emptyhanded through the shadows past this point, but rather carry cakes of honeyed barley in both hands,[13] and transport two coins in your mouth.
The speaking tower warns her to maintain silence as she passes by several ominous figures: a lame man driving a mule loaded with sticks, a dead man swimming in the river that separates the world of the living from the world of the dead, and old women weaving. These, the tower warns, will seek to divert her by pleading for her help: she must ignore them. The cakes are treats for distracting Cerberus, the three-headed watchdog of Orcus, and the two coins for Charon the ferryman, so she can make a return trip.
Everything comes to pass according to plan, and Proserpina grants Psyche's humble entreaty. As soon as she reenters the light of day, however, Psyche is overcome by a bold curiosity, and can't resist opening the box in the hope of enhancing her own beauty. She finds nothing inside but an "infernal and Stygian sleep," which sends her into a deep and unmoving torpor.