The function of the Spirit-Storage Yin Pill is similar to that of the Realm-Breaking Pill, which is to break through minor realms. One Spirit-Storage Yin Pill is enough to allow you to break through from the Middle Stage to the Late Stage of Foundation Establishment without any barrier, but it has a fundamental difference from the Realm-Breaking Pill.
The Realm-Breaking Pill increases realm levels by squeezing, tapping potential, and overdrawing inner reserves. If the foundations are deep, that's fine. If not, one Realm-Breaking Pill is enough to make one's cultivation halt for life. But the Spirit-Storage Pill is different; its function is to enhance the foundations, nourish the Spirit Root, and increase potential. With these three aspects combined, breaking through with this pill can actually allow one to progress further.
