The Elder Wand—one of the three objects that make up the Deathly Hallows and, in theory, allows a person to "cheat death"—is supposedly the most powerful wand in the world. While the other two Hallows (the invisibility cloak and the resurrection stone) are widely considered to be legends, it's possible to trace the Elder Wand through history—as its presence is often marked by bloody duels and changes of power. Its reputation is why Voldemort chooses to break into Dumbledore's tomb and steal the wand; he believes that possessing this wand will be a guaranteed way to best Harry. However, wandlore is more complicated than this: simply possessing the wand doesn't guarantee that a person will be successful with it. This suggests that there's more to winning than simply having the best wand. With this, the Elder Wand—and indeed, Voldemort's new Ministry slogan, "Magic is Might"—come to represent how limited and incomplete Voldemort's view of power and success is, as the wand is useless without a firm understanding of the theory to back it up.
The Elder Wand Quotes in Harry Potter and the Deathly Hallows
"And his knowledge remained woefully incomplete, Harry! That which Voldemort does not value, he takes no trouble to comprehend. Of house-elves and children's tales, of love, loyalty, and innocence, Voldemort knows and understands nothing. Nothing. That they all have a power beyond his own, a power beyond the reach of any magic, is a truth he has never grasped."
"So Voldemort, instead of asking himself what quality it was in you that had made your wand so strong, what gift you possessed that he did not, naturally set out to find the one wand that, they said, would beat any other. For him, the Elder Wand has become an obsession to rival his obsession with you. He believes that the Elder Wand removes his last weakness and makes him truly invincible."