Lin Feng didn't stop and initiated the breakthrough.
Every major realm brings a major change in the body, especially core formation onwards.
Spirit Origin Realm brings another change, not in the body but in the nascent soul itself.
Just like how there is a dantian for spirit qi, a blood core for blood qi, the spiritual qi needs a medium too, and this was formed at the Spirit Origin Realm.
As the breakthrough proceeded, a small core started to form inside the dantian of the miniature figure. It was similar to core formation, but this core formation was happening in the delicate soul, so even Lin Feng had to pay a little attention here.
His body was going through a tremendous change too. His senses were sharpening. His muscles and bones were getting refined one more time. It was the effect of his breakthrough in the Body Ascension Stage.
