Lyric discussion by CamelCamelCamel 

Florence Welch is a celebrity Doctor Who fan, and I have to say, these lyrics are PRETTY perfect, if too obvious, for the recent (and pivotal) episode, A Good Man Goes to War. In it the Doctor collects five allies to rescue a sixth (making seven total) from a religious sect and an entire army organized and trained specifically to fight him ("a thousand armies couldn't keep me out") based on their Doctor myth that reputes him to be a supernatural evil (making all the religious imagery in the song sort of a mockery). The Doctor's uncharacteristic anger and ego is a central issue to the story, which would fit the dramatic statement "I've come to burn your kingdom down."

The rest are spoilers for the episode and season, so I'm separating them. Don't read unless you've seen at least the six episodes preceding A Good Man Goes to War!

The season's subplot is, of course, the impending death of the Doctor, so "I'll be dead before the day is done" fits. And this is probably just a coincidence, but the big surprise twist finale of the episode reveals that the baby "Melody" ("it's a melody") goes on to become the woman "River Song" ("and no rivers and no lakes can put the fire out"), AND one plot point involves a language issue that confuses the word "pond" with the word "river." Like I said, probably a coincidence, but if Florence was going to drop hints, those would work.

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