1. Treasure Cave consists of 50 floors with each floor having 10 tiles. Use shovels to dig for rewards. If a tile proves to be an entrance, all remaining tiles will be dug up automatically without shovel consumption and you’ll be teleported to the next floor.
  2. The higher the floor, the more the shovels are requiered for each dig.
  3. Choice chests will be claimable after you clear a certain number of floors.
  4. Unused shovels will be saved for the next event.

You can obtain shovels with Daily Quests and using Diamonds (which counts on Diamond Expert Event).