A green material chest is an item in Evony TKR (The King's Return).
The description of Green Material Chest in Evony TKR says:
Open to receive a random lv2 Equipment material.
Green Material Chest is known to potentially be obtainable from opening Medium Alliance Boss Package, Lv3 Boss Monster Chest, Lv4 Boss Monster Chest and Lv5 Boss Monster Chest. The links for each item are below:
Note: This list may be incomplete.