ON GUARD. Long before Harry Potter confronted him to reach the Sorcerer’s Stone, three-headed Cerberus stood watch on the river Styx, where he prevented the living from entering the underworld. At Marisa he appears to the right of the door to the main chamber in Tomb I. In Greek lore besting Cerberus was a feat worthy of only the greatest heroes: The demi-god Hercules had to do it as the last of his 12 labors, and, thanks to his protective lion-skin cape, he was able to choke Cerberus into submission. The love-struck Psyche charmed the dog with magic honey cakes as part of her own trials. Orpheus, seeking to recover his beloved Eurydice from the dead, used his lyre to charm Cerberus and put him to sleep.