The drops are split up into four different classes. Aside from your Common drops, you can also get Rares, Epics, and if you are especially lucky, Legendary drops.
Each loot box has a guarantee of at least one rare quality item or better. Which means that you have a chance of getting four legendary items, but worst case scenario you would get a rare item and three common items.
So keep opening those boxes – and if you decide to quit, sell your account (with all the legendary items you have). Last I checked, one hard to get legendary item priced an account at $40 on a gold selling site. Good luck!
