Potter fans and scholars have noticed that Deathly Hallows bears a number of allusions to the King Arthur legends, most notably in Harry’s retrieval of the Sword of Gryffindor from the frozen lake as an allusion to Excalibur being delivered from the Lady of the Lake to Arthur. But there is another Arthurian connection I want to briefly draw our attention to.
Neville and Harry are doppelgangers of a sort. Neither is evil, but they are prophetic “twins,” as Trelawney’s prophecy could have applied equally to Neville and Harry. Thus, their fates are intertwined, in a way. Deathly Hallows tracks Harry’s final growth into a man, and so too Neville leads the Hogwarts front of the resistance, suffering the brunt of the punishment in the stead of the other students. So too, Harry kills Horcruxes, and so Neville also kills a Horcrux. And this is where the Arthurian allusion comes in.
When Neville kills Nagini, he kills a Horcrux, an act that sparks the battle of Hogwarts. In Malory’s King Arthur stories, the final battle between Mordred and Arthur is sparked when a knight on the battlefield draws his blade to kill a serpent in the grass. They had been ordered not to draw their weapons, as any such act would be a signal of aggression. The knight spies a snake in the grass, and so draws his blade and slays the snake, but, as warned, this is taken as an act of aggression and Mordred’s knights attack, initiating the slaughter that also fatally wounds Arthur.
Thus, in Harry Potter, Neville stands as the Arthurian knight who draws his blade and kills a serpent, by which act the final battle is initiated. Harry, as Arthur, has already been fatally wounded in the Forest and returned to life from his “avalon” of sorts.