The only way to live is by swapping [Spirit].
This means that under fixed spiritual intensity, the number of times a Believer uses [Spirit] is limited, and even if nothing is done, this Erosion Level will gradually increase over time.
In a situation where the spiritual limit cannot be transcended, the lifespan of a Believer, from the moment they obtain [Spirit], has already begun its countdown.
Each use of the power of the Spirit intensifies the progression of this countdown.
It is almost a dead end.
Hence, the operation of swapping [Spirit] was devised.
Before reaching one's personal Erosion Level limit, a Believer must find a new [Spirit], expel the old [Spirit] from the body, and accept the new one.
This operation is also extremely complex, as the old [Spirit] will not willingly give up the flesh about to be served to it, and the new [Spirit] may not necessarily be willing to form a contract.
