Harry Potter: 10 Dumbest Things Voldemort Did

7. The Cave's Inadequate Protections

Again, we return to the idea of the Dark Lord being needlessly complex in his plots, though you can sort of understand why he'd try as much in the case of protecting his Horcruxes. Or one of them, since the other ones he just sort of doesn't bother nearly as much with.

That being said, the entire structure of the protections on the locket is deeply flawed because of Voldemort's blind-spots. He thinks hat because the boat used to ferry any intruder across to the Drink of Despair could only carry one adult wizard, he's safe from anyone helping them. He overlooks the possibility of children, goblins, house-elves, Animagi... All manner of things, because he's arrogant and idiotic.

But even worse, he actually uses a house elf - on Regulus Black's cunning volunteering of Kreecher - to test the defences and then simply assumes that he perished and never checks, missing the fact that he could disparate. Voldemort's unwillingness to follow things up or to accept that "lesser" beings have greater or unknown powers led directly to his ruin.