Friday’s riddle features the moment in which Harry Potter looks into Dumbledore’s pensieve to see the memory in which Tom Riddle is shown the Slytherin locket ... be used as Horcruxes later ...

In a Reddit thread titled "Why Kreacher the elf is such a prick," people believe Kreacher acted terribly because of the Salazar Slytherin locket horcrux. He lived with the locket in the same house ...