Sensing that their tale of warring kingdoms, epic power struggles, and torch-lit battles could use a little bit of, y'know, bombast, naturally HBO went straight to Florence + The Machine, whose “Seven Devils” in this latest preview provides all the pomp and sweep that the first Season Two trailer sidestepped in favor of slowly building atmosphere. This time around, the swords are swingin', the explosions are explodin', everyone’s coming right out with their perfectly articulated nasty threats, and the show is working overtime to impress upon you the fact that anyone can die, just in case you didn’t already get that from the first season. And given that the tagline for its April 1 premiere is “War Is Coming,” you should probably take that to heart.