The Nian Chest is a limited time chest which was available from 30th January 2014 to 5th February 2014. It's related Epic Boss is the Nian.
The new armor introduced with this chest is the Armor of the Komodo. Opening 11 chests you receive 5 Earth Fusion Boost Armors. Opening 40 chests you receive 20 Earth Fusion Boost Armors and a Clayplate Mantle+
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Armor of the Komodo is in the Nian Chest
Clayplate Mantle is actually water/earth