There was a lot of conversation about the Deathly Hallows, so I've moved this part to the discussion page:
Grindelwald stole the Elder Wand — it only works if you beat the guy wielding it in a duel. Dumbledore was thus able to use it properly after beating Grindelwald, but for Grindelwald it was just a regular wand, maybe slightly better than normal. It doesn't work for Voldemort because he was simply given it by Snape, and he kills him to attain mastery. That doesn't work either because though Snape killed Dumbledore, it was actually Draco who disarmed him. Thus if Draco wielded the Elder Wand after that he would have been very powerful indeed.
"It only works if you beat the guy wielding it in a duel" is fanon; the book never says so. (I have to admit, though, the wandlore is by far the most confusing and unsatisfactory part of the book.) It's never stated that it was "just a regular wand" for Grindelwald; actually, it's implied that he was the true master, otherwise it couldn't have been passed on to Dumbledore and then Harry. (So, how Dumbledore managed to defeat Grindelwald is unexplained; but presumably, as someone on the page noted, the wand is simply not quite as invincible as the legend claims.) Finally, Harry takes mastery of the Elder Wand from Malfoy by physically stealing Malfoy's main wand; he doesn't disarm him in a duel.
There was a lot of conversation about the Deathly Hallows, so I've moved this part to the discussion page:
Grindelwald stole the Elder Wand — it only works if you beat the guy wielding it in a duel. Dumbledore was thus able to use it properly after beating Grindelwald, but for Grindelwald it was just a regular wand, maybe slightly better than normal. It doesn't work for Voldemort because he was simply given it by Snape, and he kills him to attain mastery. That doesn't work either because though Snape killed Dumbledore, it was actually Draco who disarmed him. Thus if Draco wielded the Elder Wand after that he would have been very powerful indeed.
"It only works if you beat the guy wielding it in a duel" is fanon; the book never says so. (I have to admit, though, the wandlore is by far the most confusing and unsatisfactory part of the book.) It's never stated that it was "just a regular wand" for Grindelwald; actually, it's implied that he was the true master, otherwise it couldn't have been passed on to Dumbledore and then Harry. (So, how Dumbledore managed to defeat Grindelwald is unexplained; but presumably, as someone on the page noted, the wand is simply not quite as invincible as the legend claims.) Finally, Harry takes mastery of the Elder Wand from Malfoy by physically stealing Malfoy's main wand; he doesn't disarm him in a duel.