A chinese mask is an item in Evony TKR (The King's Return).
Chinese Mask is one of the collection items in the exhibition for the Art Hall. It is one of four parts in the Mask Hall. After the set is completed at three stars, you can trade additional Chinese Mask fragments for gold.
The description of Chinese Mask in Evony TKR says:
Masks from different cultures. The important exhibits in Mask Hall.
Chinese Mask is known to potentially be obtainable from opening Artwork Fragment Chest V and Artwork Fragment Chest VI. The links for each item are below:
Note: This list may be incomplete.