The latest season of ranked play in Hearthstone
is coming to a close
in just a few short days on August 31. This month's participation reward is the Chill of Icecrown card back seen above. You only need to hit rank 20 before the end of the month to earn the skin, which isn't a particularly difficult task. Losses prior to rank 20 don't cause you to lose ranking, so as long as you play enough to work your way up to that point, you have it in the bag.