Unusual Chests are chests that contain randomly generated items with enchantments and rarities. Generate as many Unusual Chests as you desire, but you'll need to find the right material to act as a key in order to open the chest. Give Unusual Chests as rewards to your players, and watch them scour your server to find keys to get their loot.
For uChests documentation, setup guides and additional information, please see the uChests Wiki