Or in other words, a spirit universe, once opened, is not absolutely incapable of being upgraded again.
There is also a type of hidden advanced universe that appears to be a low-level universe on the surface and is considered a low-level universe when opened, but in reality, it is a high-level universe. After opening, it can still break through new Layered Heavens and grow again.
Such universes are extremely rare, but Lin Yun had heard of them when he was the crown prince of the Divine Clan.
These hidden advanced universes do not necessarily reach the highest level of eighty-one Layered Heavens; they may only achieve sixty-three, or seventy-two, or even just peak at fifty-four Layered Heavens.
