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After managing to Integrate the four Spirits into the System, I was able to see their Abilities in more detail and even their Skills and so on, which made things more fascinating than I imagined. Also, they were capable of gain Item-like Enhancements, giving them amazing new effects to their abilities, ways of fighting, and so on.
Once I was done, I let them practice and playing with their new abilities on the open field, even Rose who was a rather reserved adult woman resembled a child playing with her new powers, she seemed to like it a lot. The Divine Monsters of the open world area of the lobby didn't like it that much though.
In the last thirty minutes I tried doing more System Integration and Upgrade on other people, then moved on to my Divine Weapons and Equipment, and it didn't seem to work either. whenever I tried, I would get a notification saying I needed specific enhancement items instead, but I had run out of them already.