The Cosmos Chest is a limited edition Chance Chest that was released on July 17th, 2014 and ended on July 22nd, 2014. The new Epic released in this chest is the Gold Chromatic Mantle which is an Epic Starmetal Armor.
1 Chest: 45 Gems
11 Chests: 450 Gems
40 Chests: 1,400 Gems
11 Chests: 8 Air Fusion Boost Armors
This is the first Chance Chest which has a Fusion Boost Armor that doesn't match an element of the Epic Armor, since Gold Chromatic Mantle is a Starmetal Armor, and there are no Starmetal Fusion Boost Armors