Michael had to give Zeke and Kaleb another Soultrait Symbol to fill the gap caused by the chunks of the souls he and Fenrir had cut out of them. The process was not as delicate as Michael hoped, but it worked better than anything else. Filling the gaps with a 5-Star Soultrait Symbol and infusing more SoulStar Fragments into them seamlessly to tend to the woundsz.
If not for that, both Zeke and Kaleb couldn't be saved. Their situation was already bad as it was. The Blood Incursion worked stronger on them because their bloodline wasn't tarnished. They were pure humans, which amplified the effects of blood incursion.
Thus, chunks had to be cut out of their souls, and the Needle of Lost Memories had to be utilized more often than Michael had wished. That was not only annoying but caused some trouble as well.