Eldritch Horror Insert: - Rules of Play says:
This insert is designed to be compatible with Eldritch Horror®, and includes space for a single small box expansion (in these images the Forsaken Lore® expansion is in the box). 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 boards and player boards act as a lid on top of the trays.