Keys, Legendaries and Up

In the game menu, it says keys are found in battle. I have never seen one drop. Is this a blatant lie??? Also, I have never found Legendary or Unique in battle, only in the 100 soul chest in the Shop. Do these drop, or can only be bought? Thanks for your info.

Keys only drop on arena. Legend equip drop normally while I farming locations. Unique equip drop only on shop

oh, ty for this information