Crystal Tears is a special resource that you can obtain for completing the Maze. They are needed for unlocking unique upgrades for your dungeon. You can find these upgrades and see how many  Crystal Tears you have in the dungeon upgrade menu. The more health you have when you reach the chest at the end of the Maze, the more  Crystal Tears you get. For example, if you finish the Maze with 3 stars, you get 15   Crystal Tears, and if you only manage to get 1 star, the reward is just 5 Tears. Moreover, each time you reach the chest in the Maze, you will have a chance to win additional rewards, such as orbs, gold, keys and more  Crystal Tears using the spinner.