Iskall's Treasure Island is a shop in the Season 7 Shopping District run by Iskall85. It sold the shulker boxes or 'gems' from the left pile that contain something random for a diamond block. To pay, the diamond blocks are placed onto the right pile.
The island was later converted to be a sign up for another game where hermits would buy a shovel, called spoons and use it to hunt for treasure on a separate island. The golden shovels have varying levels of durability and the hermit gets to keep any item that they find on the island. The new version was so profitable that on his first full day he made a full barrel of diamonds.