Leaving the north, this second trailer goes through several shots of this season's key players: Cersei, preceeded by Gold Cloaks marching in the capital; Daenerys in Dragonstone, stroking the length of her new map table; Theon and his few surviving Ironborn coming ashore (more of that later); a lonely shot of Ayra on horseback; Jaime walking the castle walls of maybe Casterly Rock, maybe Highgarden; Littlefinger creeping; a sword being sharpened.
This succession of shots along with those of our northern characters serves as something of a primer for the plot lines season 7 will follow. Cersei continues to rule, albeit just barely, in King's Landing (also note this is her sole appearance this trailer). Daenerys has finally arrived in Westeros, but now she must learn as much as she can about the land she wishes to conquer. Yara's fleet is expected to cross paths with that of her uncle, Euron, and the battle does not appear to go her way; Theon, however, escapes. Arya remains Game of Thrones' lone wanderer, though that may end this season. Jaime will either be sent to sack Highgarden, the seat of House Tyrell, or to defend Casterly Rock, the Lannisters' ancestral home, or both. Either way, season 7 will again see Jaime on the battlefield at his sister/Queen's behest, fending off attacks from their many enemies. Littlefinger will continue to the play the game as best he can and always from the shadows, but we may see his luck run out this season. Maybe that next shot of the sword is suggesting his days are numbered?
Over the next succession of shots -- which include Daenerys walking the beach of Dragonstone; her entering the castle with Tyrion; pulling down Stannis' flaming heart banners; her now very large dragons flying over the bay; Tyrion watching from the cliffs; Theon in shadow and flame; a helmeted Grey Worm in a boat; Brienne and Podrick in a snowy courtyard; and the Hound in the midst of a snowy battle -- Jon provides the voice over: "For centuries our families fought together against their common enemy. Despite their differences, together. We need to do the same if we're going to survive, because the enemy is real."
What Jon is obviously pitching here is the alliance needed to fight the Night's King and his army of the dead. That's the real enemy, and no other leader is more aware of that threat than Jon. It's expected we'll see him reach out to the newly arrived Targaryen conqueror, and that may in fact be who he's speaking to here. The following shots seem to back up the assumption, showcasing the team players from each side -- Tyrion, Grey Worm, and Theon from the Targaryens, Brienne and Podrick of Team Stark.
However, the wild card is Sandor "formerly the Hound" Clegane. Season 6 saw him join up with the Brotherhood Without Banners and they'll be traveling north to fight the White Walkers themselves. That puts him right in the heart of the great war, but after the Brotherhood inevitably fail in their attack on the White Walkers, who will he align himself with next? (Assuming he survives, that is.)