The Great Masters had used the pit as a prison. It was large enough to hold five hundred men… and more than ample for two dragons. For how long, though? What will happen when they grow too large for the pit? Will they turn on one another with flame and claw? Will they grow wan and weak, with withered flanks and shrunken wings? Will their fires go out before the end? What sort of mother lets her children rot in darkness?
"They are outgrowing the restrictions that she’s placing on them. She’s always feared it. I mean, for goodness sake, they’re dragons. They’ve killed her enemies; what’s going to stop them from killing anyone? I think it’s kind of a symbol of her losing control of herself, and losing control of what she’s doing." — Emilia Clarke on Daenerys Targaryen in the Season 4 Foreshadowing