Thread:Silver-Haired Seireitou/@comment-18812574-20141229072941/@comment-2089817-20150102165002

The soul fragment would grant a Fullbringer (or any soul for that matter) something that "they lack"; something that, in their heart of hearts, they know they desperately need for some reason. In the time of Yhwach's childhood, that is what his soul portions did, but on an arguably smaller scale. The fragment would resonate with their soul and respond to that need, granting them whatever power they were in need of; the exact same result you're trying to get (at least the way I read it) with the whole Fullbring tugging on the soul fragment thing.