Regulus Arcturus Black was tragically killed by the Inferi in the hidden, underground lake within the Horcrux cave. His death occurred during his brave, albeit ultimately unrecognized, mission to sabotage Lord Voldemort's immortality.
The Treacherous Cave and the Potion
Regulus, deeply disillusioned with Lord Voldemort's dark path, had chosen to betray him by attempting to destroy one of the Dark Lord's most potent Horcruxes: Salazar Slytherin's locket. This dangerous quest led him to a desolate, booby-trapped cave. To reach the locket, he had to consume a powerful and torturous potion designed to protect the Horcrux. This dark magic induced an excruciating, unquenchable thirst, leaving him gravely weakened and desperate for water.
A Heroic Sacrifice
Despite his rapidly deteriorating condition, Regulus managed to secure the real Horcrux. In a pivotal act of defiance, he bravely switched the genuine locket with a fake one, which contained a message for Lord Voldemort. Before facing his ultimate demise, he ensured that the true Horcrux was safely removed from the cave, entrusting it to a loyal companion and securing a solemn promise of absolute secrecy regarding their perilous mission.
The Inferi's Grasp
Weakened by the potion and driven by an overwhelming, agonizing need for water, Regulus crawled towards the dark, icy lake at the center of the cave. As he attempted to drink from its depths, the chilling, reanimated corpses known as Inferi emerged from the water. These guardians of the Horcrux, animated by dark magic, mercilessly dragged Regulus beneath the surface of the lake, where he drowned and perished. His final act was a selfless sacrifice, a courageous blow against the Dark Lord's immortality.
