Is Beric's sword the legendary "Lightbringer"?
Westeros' favorite story, the legend of Azor Ahai, tells of a brave warrior who ended the first Long Night -- a generations-long war against the White Walkers -- by using a flaming sword named Lightbringer to mow down the ice zombies. Lightbringer was an average sword until Ahai used it to kill his wife, Nissa Nissa, which imbued it with a sacrificial magic powerful enough to defeat the enemy of men.
The Lord of Light's followers believe that Azor Ahai will be born anew and once again save mankind from White Walkers. This also means a reforging of Lightbringer. But as with all prophecies, interpretations vary. Some fans believe a literal Lightbringer will show up again, while others think that Daenerys's dragons might be their own kind of "flaming sword," a fire weapon that we've already seen take out an army of wights.
But if we're going the literal route, it's possible Beric fits into the prophecy. We've seen him light swords on fire before – during his duel with the Hound, he set a spear ablaze, though it was shattered in half. It's unclear how, exactly, he's able to do this. Maybe it's doused in something (in the books, Thoros is known for lighting swords with wildfire) or maybe it's a special present from the Lord of Light.
Assuming that Jon is Azor Ahai reborn, it's possible that Jon's proximity to Beric and his fire sword is a sign that he'll inherit the trick himself. Could we see a flaming Longclaw before the series is over? Crazier things have happened.
Whatever the case, Jon and Beric seem locked by fate. George Martin blew everyone's minds when he recently referred to Beric as a "fire wight," which makes Jon one as well. Will these two fire wights continue to sound off against their icy brothers? Now that Thoros is dead, they better get going while they still can, before that pesky enemy Death catches up.