Warning: spoilers for season six Game of Thrones ahead, duh.
A recent Game of Thrones fan theory has some interesting thoughts about Cersei, her intentions, and her future. And while every episode opens up new opportunities for guess work and theories, this one actually draws on several clues from earlier seasons.
Cersei learned in the most recent episode that trial by combat is now outlawed, rendering her sure bet—The Zombie Mountain—as useless in her defense. Yet mad scientist Qyburn did bring her some good news: he looked into that thing they talked about, and there's plenty more of it. While they sound like mobsters speaking in code on pay phones, it's almost certain they were talking about stashes of wildfire leftover by the Mad King.
Reddit user Greys88 laid out one of the more convincing fan theories, that Cersei will burn some stuff to the ground using those hidden caches. At the very least, she'll target the Faith Militant (and perhaps much of King's Landing by accident). Viewers already know, from some of Bran's visions earlier this season, that the Mad King stored lots of wildfire around King's Landing. Apparently, Qyburn just confirmed that it's a whole bunch.
The theory notes that Cersei has previously threatened to burn cities to the ground for her children on several occasions.
Additionally, way back in season two, Daenerys had a vision in the House of the Undying which appears to show a torched King's Landing:
There's just one problem for Cersei and her plan of arson: her last surviving child, King Tommen, is tight with the Faith Militant and could accidentally be burned along with her enemies. And that's where it gets really interesting. The loss of her last child could drive Cersei towards madness. Madness and a desire to burn a bunch of people with wildfire is what led to the death of the Mad King, at the hands of none other than Jaime Lannister.
So: if Cersei burns King's Landing and runs, she may later be killed by Jaime. As Greys88 puts it, "Jaime will end up killing Cersei to smooth over relations with the Tyrell family and because she killed their last child."
He would then have killed the Mad King that threatened to burn everyone, and the mad "queen" that actually went through with it. And that would conclude the sad, tragic story arc of Cersei Lannister.
This theory, though, is for now just a theory. It's still not clear what's actually going to happen with that secret stash of wildfire, but you've got to think it's going to burn lots of people, and lots of things, at some point. Otherwise, what's the point?