Testament to the international and unyielding popularity of Game of Thrones, it seems some of the show's biggest fans also happen to be serious soccer supporters of supportive banners that could ever complement a sporting battle such as this. Unless of course the players they're trying to motivate don't actually watch the show, and instead of being rebel-roused toward victory they just got confused and kicked the ball at some unsuspecting water boy's head.
If you do watch the show (you don't? Um, stop reading, go watch all five and a bit series' and then come back to us) you'll appreciate just how significant it might be to have Night's King by your side as you face your greatest opponent, scary looking bastard that he is.
If you watch the video, you might notice that it looks as though the dude is either dancing ('throw your hands up in the air', etc.) or squaring up to somebody. Either way, it's pretty cool.