Since Michael decided against picking Soultrait Symbols after advancing to the 1st Tier, ensuring his War Rune would be refined quickly, he picked up a few mountains of Spirit Armaments, Artifacts, and some items like the Orbs of Growth.
Michael never lost control of the Extraction Seed's powers, which was also why he could still use Insert. The Soultrait Symbol of Insert was no more but the powers still existed within Extraction. Therefore, the secondary body could use Insert as well.
He used Insert to combine the mountains of Spirit Armaments and Artifacts by mixing some of their strongest traits. He fused the common traits to upgrade them and didn't waste any time creating some of the strongest Artifacts he had ever held. Interestingly enough, Michael had to use Extraction on a few Divine Artifacts to remove their most precious parts, which he then fused with the Orbs of Growth.