Generally speaking, whether it's a Curse Mage or a Curse Master, including the Curse Spirits, any mage capable of deploying a domain will construct their domain into a closed boundary.
This is to prevent anyone from leaving the domain and escaping the coverage of the domain.
Only when within the domain can the domain deployer gain a power boost, and only within the coverage of the domain can their art be an absolutely accurate force.
If people could easily leave the domain, then this power would not hold much significance.
Therefore, most domains are closed, including Reiger and Gojo Satoru's [Infinite Void], as well as Shinobu's previous [Self-sealing Sphere]; once a domain is deployed, it's extremely difficult for those inside to escape.
But Ryomensukuna's [Domain Expansion: Malevolent Shrine] is different.
