Chests play a major role in Clash Royale deck building with the gold, gems and cards they contain.
As far as I know, this chests drop randomly. It has a small chance to replace a chest in the pattern above. The chance of replacing Magical Chest and Giant Chest is higher than replacing Gold and Silver Chest. Players who get it in place of a Silver or Gold is extremely lucky!
Exactly there is a chest order in game. Every Chest that you get after the Battles is based on this list. When this cycle goes through, it will restart again.