This insert is designed to be compatible with Mysterium©, and the Hidden Signs© and Secrets & Lies© expansions. There is space also for any promo cards you might have. The design provides both efficient storage and improved game play. Many of the trays can be utilised during the game, and they greatly aid set-up and clear-away times. The rules and boards act as a lid on top of the trays. There is space for all cards to be sleeved.