Speaking about the big battle sequence of Season 6, showrunner David Benioff told EW: "Miguel did such a fantastic job with Hardhome we thought we should bring him back this time with horses. Horses are not easy, at all..." Here we get to see those horses in action, first lined-up and raring to go, and the next in full-flow. It's not entirely clear who is riding them at this point, but it seems a given that it's the army opposing the Boltons, which would mean some combination of Northmen and wildlings.