The Personal Chest is a chest that can be created at the Novice Crafting Bench with 25 Shapestone and 50 Flux. Once created, it can be placed on a Cornerstone or in a Club World, if you have sufficient privileges for building/placing blocks.
Items placed in a Personal Chest are available across worlds and can be accessed at any cornerstone with a Personal Chest. As such, placing additional chests will share the inventory across all chests rather than a separate inventory for each.
The Personal Chest has 50 slots by default. Additional space can be purchased 50 slots at a time for 1,200 1,400, and 1,600 Credits from the Personal Chest menu. The maximum Number of slots is 200.