The Pocket Dimension (a.k.a Autonomous World) is a storage dimension created by cultivators at the Sovereign Profound Realm and above. Its size depends on the profound strength of the cultivator and third parties can break the pocket dimension of a cultivator if they are stronger.
Low-level profound practitioners used spatial rings as storage devices, but once one reached the rank of Monarch, one could open a personal dimensional pocket. One could store important objects in this dimensional pocket, so that these things would not be so easily lost or stolen like the objects in a dimensional ring.Stealing something from someone’s dimensional pocket was far harder than killing that person. If one truly killed that person, his dimensional pocket would collapse as well, and the items inside that pocket would either be ripped apart by the spatial energies or fall into the cracks between dimensions. Either way, those items would never appear again.