BuzzFeed discussed a fan theory that Daenerys Targaryen may not end up being the fan favorite savior many expect to sit the Iron Throne. The theory focuses on a rousing speech she gave in the last episode, plus a close look at some very brief visions from Bran. Warning: as always, spoilers for the most recent episode ahead.
The end of the most recent episode had Daenerys riding Drogon, and giving a fiery speech to the Dothraki. She declares for the first time that she will soon head to Westeros.
So, the latest fan theory suggests that her enthusiasm to take the seven kingdoms reveals vulnerability in the form of her father's madness, and that she may end up the villain instead of the hero. Just like papa, she could become too ruthless with anyone that stands in her way—maybe even too bloodthirsty. So instead of continuing to unify on her way to the top, she could recklessly destroy everything instead.
The theory is supported by a look at Bran's warging visions from the beginning of the episode. They show her father, the mad king, and his obsession with wild fire (which he used to burn anyone who disobeyed his rule). The vision also showed his demise at the hands of the king slayer, Jaime Lannister.
Additionally, there are a few snippets of a dragon (probably Drogon), and what appears to be a dragon shadow over Westeros. That could support the theory that she destroys Westeros instead of taking the throne. Of course, the dragons could also come in peace.
A closer look at the visions reveals much more than just her capacity to become a mad villain like her father. The flashes also focus heavily on the White Walkers. Thus far, the TV series has shown that White Walkers can be killed by dragonglass or Valyrian steel. So it's possible that Daenerys and her dragons are the only ones that can defeat the undead and save everyone else. After all, Bran can see the past, the future, and probably everything in between.
But perhaps Bran will learn to warg into her dragons. Eh? That way even if she goes mad, her dragons could still save the world. When Bran met the three-eyed raven at the end of season 4, he asked whether he'd walk again. The response was, "You will never walk again, but you will fly."
It's not clear if Daenerys will become mad with power, or what will happen to her as she burns her way westward. What is clear is that the dragons will probably be necessary to defeat the White Walkers, because there are only a few existing swords forged from Valryian steel.