Lucky Box is a system where you can obtain specific Items at random.
There are 3 chests: a golden, a silver and a bronze one.
Each of them contains different items, the best in golden, and the worst in bronze.
You can obtain the keys through either the time-limited challenge or through buying them at treasure island at a quantity of 5(Bronze Key [50 Belly], Silver Key [125 Belly], Golden Key [500 Belly]). You can also exchange keys at Summit Arena shop at a quantity of 1 for 5 times each. (Copper [100 Honor], Silver[200 Honor], Gold[500 Honor])
[NOTE] Some items can be obtained but aren't shown in the rewards section!
Use them when it's 1.5 exp or at events to have the biggest benefit out of the containing energy.